Every year at this time, ReadWriteWeb picks out the best of the Web over the past calendar year. Our annual Best Of series will be even bigger and better than ever in 2011! We have no less than ten themed 'top 10' lists coming your way over the following four weeks before Christmas, each prepared by a different member of our writing team. We'll also survey the top trends of 2011, along with other regular features such as Best BigCo and LittleCo of the year. To kick things off, today we present our list of the 10 best social network and social media products of 2011.

Almost every Web product these days has some kind of social element. But to make this list, the product has to have social networking or community building as a core part of its offering. So without further ado, here are our top 10 Social Web products of 2011:

1. Google+

Up till 2011, Google wasn't known for its social networking prowess. Unless you count Orkut, a social network product that became a phenomenon...in Brazil only. At the end of June 2011 that all changed, with the worldwide launch of (in our opinion) the best social network product of the year: Google+.

It was a muddled launch. Back in March, ReadWriteWeb's Marshall Kirkpatrick got the scoop about a new Google product based on a circles concept. At the time, Google vigorously denied the existence of such a product. But lo and behold, Google+ launched over three months later - and its core feature was indeed "circles." With circles you could better segment your friends, something that was a major pain point in Facebook.

Initially Google+ launched to a chorus of media outlets shouting "Facebook killer." However, it soon became apparent that Google+ was going to be most useful to Google as the social component of its entire online product suite: including Google search, Google Reader and YouTube. Although it's a more than useful standalone social network, too. Particularly for topic-focused discussions. Google+ has grown rapidly, attaining over 40 million users in a matter of months - although just how many are active is a contentious point.

2. Facebook

We selected Facebook as our Best BigCo of last year, due to astounding user growth. Facebook not only continued its impressive growth over 2011, but released a number of innovative new features. Some of those announcements were spurred on by the arrival of Google+. But the important thing is that not only did Facebook respond quickly, they changed things up with a radical new design and an entirely new form of sharing media.

The new profile design was termed Timeline and at time of writing it's still in developer only release. The new type of sharing was nicknamed "frictionless sharing" and enables users to automatically post what music they listen to, what they read, and more. It has been controversial, with many people uncomfortable with how much they are sharing. Whatever the eventual outcome of Facebook's new features, it's very encouraging to see that it hasn't stopped innovating - despite having by far the largest user base of any social network, with over 800 million active users.

3. Twitter

Twitter was overshadowed a bit this year by Facebook and Google+, but it remains a force to be reckoned with as a mainstream social network. In September, it announced it had 100 million active users. It also got closely integrated into Apple's iOS 5, which among other things enabled users to tweet directly from Apple apps like Camera, Maps, Photos and Safari.

Perhaps the feature that most epitomized Twitter's continued growth as a mainstream tool was its usage with TV. Not only do many users tweet while watching television, Twitter began to partner with TV networks. For example its partnership with popular TV show The X Factor, enabling users to tweet their votes.

4. Tumblr

Tumblr is another social media product to have experienced huge growth over 2011. During the past year, Tumblr has grown from just over 100 million visits per month to over 350 million now (according to Quantcast). Tumblr gets over 12.5 billion page views per month, over 8 times more than Wordpress.com. Although we should note that Wordpress.com still gets more visits and it too has grown a lot over 2011.

Just as important as the user growth, is how Tumblr has brought the curation of content to the mainstream. Plus it's having a big impact on journalism, with old and new media brands alike using Tumblr to provide curation to their readers.

5. reddit

The Web of course is not just about reaching a mainstream audience - as Facebook, Twitter and others in our list have done. There are tens of thousands of social networks that appeal to a niche audience. Reddit is one example, although it has also shown strong growth by diversifying from its core tech-focused audience. In September, reddit blogged that it had tripled in size over the previous 15 months: "Since last May, we've grown from 7 million monthly unique visitors to 21.5 million. Our pageviews have exploded 4x to a staggering 1.6 billion pages served per month."

Part of the reason for reddit's growth are "subreddits," which the company says is "the secret to reddit's growth." A subreddit, such as DoesAnybodyElse (a place for people to talk about their quirks), is "a class of online community, just like mailing lists, forums, and chatrooms are." There are thousands of subreddits and each is "a distinct community with its own purpose, standards, and readership."

It's worth mentioning StumbleUpon here too, another "social news" service that had strong growth this year.

6. SoundCloud

One of the talking points of Mary Meeker's presentation at Web 2.0 Summit in October was the future of sound. Meeker claimed that sound would soon be bigger than video on the Web. She name-checked a startup from Germany called SoundCloud, which enables people to create and share sounds. What brings SoundCloud to the top 10 Social Web list is its very active community. SoundCloud users upload, comment on and re-share audio with a level of engagement not too far behind YouTube (which it is often compared to).

SoundCloud has enjoyed exponential growth this year. It had about 7.5 million users as at October, with 5 million of those signing up over the past 12 months.

7. LinkedIn

LinkedIn, the leading business social network, has had a good year. Its user base increased by over 60% and revenue more than doubled.

Most impressively, LinkedIn has innovated with new product lines. Apply Through LinkedIn job applications and the recently launched Classmates are two examples. The latter is a data-driven tool targeted at students and recent graduates, its biggest growing demographic.

8. GetGlue

One of the key trends of 2011 has been so-called second screen apps - mobile apps that make watching television a less passive activity. GetGlue, a self-described "social network for entertainment," is tapping into this growing market. It enables you to "check-in" to watching TV shows and movies (you can also check-in to a great range of other activities, such as reading a book or viewing a web page).

As at September, GetGlue had over 1.5M users and a database of over 200M ratings, reviews and check-ins. [Disclosure: GetGlue founder Alex Iskold was a columnist at ReadWriteWeb from 2006-09]

9. Instagram

For a service that is only available on one platform (iOS) and doesn't even have a proper website, Instagram has experienced very good growth since launching in October 2010. The photo sharing service now has 13 million users.

Photo sharing apps are a dime a dozen these days, but Instagram has managed to keep ahead of the pack despite its limited resources and iOS-only focus. It's a simple app: you upload a photo, apply some funky effects to it, then share it with the community. In short, people love the app. It will be interesting to see if Instagram can continue growing in 2012. To do that it needs to launch an Android app soon, but in the meantime its API has gotten solid take-up. See also: 6 Effective Ways to Get More Instagram Followers.

10. Meetup

Social networking used to mean getting out and meeting people in the real world. At least one of this year's top 10 hasn't forgotten that! Meetup.com facilitates offline group meetings. While it got off to a shaky start in January, with a redesign that met with resistance, Meetup has impressed us this year for its ability to connect people in real life. We have used it ourselves, to organize local ReadWriteWeb meetups. It is a well used product among a wide variety of people - for example I belong to a book club that is organized through Meetup.com.

This year Meetup celebrated its 10th birthday. Co-founder and CEO Scott Heiferman sent out an email in September, explaining how Meetup was founded after 9/11 to try and get local communities doing more together. According to Heiferman, there are now more than 10 million Meetup users and 100,000 Meetup groups.

Honorable Mentions

As always, there isn't room for every product we would've liked to include. Here are some of the ones we considered, but which didn't make the top 10: Quora (Q&A service that got a lot of interest during the first half of 2011, but has since dropped out of the limelight); Foodspotting (fun app for food photos that gained a loyal following); Pinterest (next-gen Delicious, one to watch for 2012); Foursquare (it grew a lot, but we felt it didn't quite do enough this year on the social side - although it will likely pop up in one of our other 2011 Best Of lists).

There you have it, our ten picks for best Social Web products of 2011! Let us know if you disagree with any of our choices in the comments, or if we missed one of your favorites.