There are some 225,000 mobile applications for the iPhone now and 70,000 for Android, so every so often we like to highlight a few that have caught our attention. This latest edition of our favorite smartphone apps includes a few in testing, a few we're madly in love with, some notable updates and some you may not have even heard of yet.

New & Awesome

Instagram (iPhone): OK, we're dubbing this one the "app of the month." Initially called Burbn, the original app was transformed into Instagram, a photo-sharing service and image editor. With a number of built-in filters, you can turn your iPhone photos into more attractive and interesting versions of themselves, then share them either publicly or privately with fellow app users. Your friends' photos are in a section called "Feed" and the most popular photos from across Instagram are found in the "Popular" section. While what Instagram is doing is not revolutionary, there's something to be said for a well-designed app like this. There's no learning curve here, it's easy and, frankly, it's just fun. Oh yeah, it's totally free, too. (Download)

Foursquare (Symbian): Mobile check-in service Foursquare arrived on Symbian smartphones (Nokia) this month with a version that's comporable to those on other platforms like Android and iPhone. It even includes a homescreen widget showing the most recent check-ins from your friends. (Download)

Posterous (iPhone): Minimalist blogging platform Posterous is now an iPhone app, too. The new app lets you post, manage your settings, upload media and geo-tag your updates. (Download)

Tango (iPhone, Android): After a notable WSJ debut, Tango has proved that good press matters. The app was downloaded 1 million times in its first 10 days of release. Basically, Tango is like FaceTime, Apple's somewhat crippled iPhone 4 video chat feature, but works across iPhone and Android and over 3G, 4G and Wi-Fi. (Download iTunes, Download Android)

SwiftKey (Android): Released from beta at the end of September, this stock keyboard replacement learns how you type and suggests words for you that you can include in your email, text, etc. with just a tap. For anyone who feels fumbled-fingered on touchscreen keyboards, this app is a real time-saver. (Download)

Wolfram Alpha (Android): Computational search engine Wolfram Alpha arrived on Android this month, and like its iPhone counterpart, the app is only $1.99. With this app, you can use Android's voice input to get answers to your factual questions. (Download)

Instant Heart Rate (iPhone/Android): The app everyone is trying this month. Supposedly, this app can measure your heart rate just by you placing a finger over your camera's sensor for 10 seconds. The app's homepage says it tracks the light that passes through your finger and that works because, with every heart beat, your blood becomes more oxygen-rich which causes a slight change in the color of your skin. It actually appears to work, too, but we might have to check with our doctor on that (wink). (Download)

In Testing

Marco (iPhone): Marco uses SMS to connect smartphone users to a shared map. Think of it sort of like a Google Latitude-like service that doesn't require the other user to be on Latitude - you can just send someone a text instead. The recipient doesn't need the app for this to work, either. (Download)

TabbedOut (iPhone): Sadly, we can't test this one ourselves because our favorite local restaurants aren't supported, but maybe you can try it for us and share your thoughts in the comments. This startup out of Austin, Texas, lets diners and bar-goers pay their bill via their iPhone. It's live now at Texas hotspots like The Mohawk and The Blind Pig Pub in Austin, Lakewood Bar and Grill in Dallas and Broadway Heights California Cuisine in Chico. (Download iTunes, Download Android)

AudioPress (iPhone): This app manages podcasts and Internet radio stations, the former so you can stop worrying about syncing your iPhone with iTunes and the latter because we all love Internet radio. But what's also cool about this app is that it offer audio articles too, provided by launch partner the Associated Press. These news articles are read aloud - by humans! (Download)

Paperlinks (iPhone): What do you get when you combine QR codes with formal (paper-based) invitations, announcements and other sorts of greeting cards? A pretty nifty way to modernize your next invite. From the online stationary store Paperspring you can order and customize invitations which include a barcode linked to the company's iPhone app. Scan the code with the app and you have a digital invite, complete with photos, videos, comments, an RSVP form, maps, and more. (Download)

Geomium (iPhone): Because the world doesn't have enough check-in apps, right? Launched at the end of September, the app is more of real-time Foursquare competitor and friend locator, plotting your friends on a map. Traction? We're not betting on it, but if you have an LBS obsession, this is a new and fun app to try. (Download)

Updates Worth Noting

PayPal (iPhone): At the beginning of the month, PayPal announced its PayPal Mobile for iPhone app had been updated with a new feature called Mobile Check Capture, which allows you to snap a photo of a check and have the money deposited into your PayPal account. Technology that saves us from running to the bank is awesome. (Download)

Skype (Android/iPhone): Although we're happy that Android users everywhere can now download Skype, and not just Verizon Android users, we were bummed to find out it was Wi-Fi only. Good thing there's a hack for that. Skype also just updated its iPhone app to support a new settings option that lets you choose its offline behavior - either it's always running in the background, never running in the background or you can specify how long it runs in the background before going "offline." That's definitely going to save on battery life. (Download Android, Download iTunes)

TweetDeck (Android): Android's version of TweetDeck 1.0 just went live today in the Market, bringing a stable version of the popular Twitter-watching application to all Android users. But while the name implies the app's focus is Twitter, it actually supports viewing and posting to Facebook, Foursquare and Google Buzz, too. (Download - scan barcode!)

WeatherBug (Blackberry): Blackberry users are all about the data, right? Well, for those who like Weatherbug's apps, those got a big update at the end of September. Now the design has been improved, weather content is better and you can finally get weather alerts for your city. (Download)

Waze (Android): The popular "social driving" application was updated to version 2.0 on Android this month, allowing users to participate in driving groups, the mobile commuter gatherings that add the "social" element to this mapping application. Bug fixes and stability improvements have been added as well as multi-touch support, zoom and rotations. (Download)

Google Goggles (iPhone): Technically, a feature within an app, Google Goggles for iPhone is the iPhone port of the visual search technology Android users have had for some time. With Goggles, a part of Google's Mobile App, you can take a picture of an object and get back Google search results. (Download)

Netflix (iPhone): The Netflix iPhone application was updated to a new version this month which supports "video out" on the iPhone 4 and the 4th generation iPod Touch devices. That means that Netflix subscribers can now use the app to stream the on-demand programming from their mobile handheld to their TV set using a connector cable like this one. (Download)

Google's Car Home (Android): Google updated its "Car Home" application which provides big-button access to the phone's features for use with a windshield/dash-mounted device. In the new version, there are app shortcuts galore, customizable icon colors and new background wallpapers. App shortcuts are supported too and the app can be configured to automatically launch when placed in a dock. For similar features, Sprint/Froyo users can use Vlingo's new InCar app instead, if they prefer. (Download)