Recently I posted a meta-list of Web 2.0 lists. My current favorite list is the eConsultant's Web 2.0 Directory. It has "1007 Web 2.0 sites/services/links in 50+ categories". Sacred Cow Dung's is another easily-scannable catagorized list. As I scrolled through these lists today, I wondered which categories are currently underserved by products/services... We all know there are tons of social networking sites, photo services, online calendars, etc - a new contender in any of those popular categories seems to come into my inbox every second day. Frankly the world probably doesn't need yet another blog search or photo-sharing service.

So what market segments are in need of more products to fill them out? Here are ten I identified from eConsultant's list, but I'm keen to get your feedback on this. Of course I chose ten because that gives me the chance to do a 'top ten' post, a la Guy Kawasaki ;-) In no particular order, here they are:

• Community-building services - overlaps with local; examples: craigslist, backfence, Oodle. There is a lot more that can be done to bring local communities into the 2.0 digital lifestyle.
• Cooperative Distribution Services - e.g. BitTorrent; I'm no expert on P2P, but 3 products listed in eConsultant seems a little light to me.
• Financial Services - has plenty of contenders, but I read/hear hardly any buzz about them in the blogosphere; if you're talking about 'real world' needs, finances is right near the top of the list (as opposed to blogging, organizing photos, etc)
• Game Services - only 9 are listed in eConsultant...
• Grassroots Services - community and charity projects; there are some excellent services already (KatrinaList, OurMedia, etc), but again seems like a lot more could be done. You could also include Non-profit services with this.
• Mobile services - already has plenty of contenders, but I'm including it because mobile is undoubtedly going to be a growth segment as the mobile Internet matures.
• Project Management Services - even though Basecamp has seemingly a lock on this market, I'd like to see more such products from other companies. Indeed I'd like to see more innovative Web Office solutions in general - web-based office apps that really push the envelope. Like Zimbra, JotSpot Tracker, Morfik.
• Publishing Services - publishing as in paper or e-books... now this is really a market I'd like to see others enter; Lulu.com is my current favorite. e.g. how about a service that lets people create their own PDF books or reports and charge for them on a website (a la the 37Signals book)?
• Streaming Services - i.e. Online media/music/video streaming services; this media market looks ripe for growth.
• Wi-Fi Services - only two listed in eConsultant so far.

Those are my initial selections, but interested to hear some feedback about what web 2.0 markets you think are underserved - and perhaps under-hyped (yes there is such a thing).