Quora is a new (private Beta launched in January, with general availability in June) social networking site based around questions and answers. Users ask or answer questions and then follow the question topics to see all the answers in their newsfeed. You can also follow users, a la Twitter.
Quora may not sound all that revolutionary but it seems to be pretty addictive and is gaining users like crazy. The buzz around Quora got a huge boost a couple of days ago when tech uber-blogger Robert Scoble called it the "the biggest blogging innovation in 10 years".
Quora's got a lot going for it including a clean, easy to use UI and a powerful search function. The service is addictive and seems to have a number of well known subject matter experts and tech industry insiders among its active users.
I like that Quora has a full-featured mobile webapp. Visit quora.com with just about any mobile browser or click the "mobile site" link at the bottom of the desktop Quora page to see it.
The mobile version of Quora lets you see and do almost everything you can on the full site including registering for an account, viewing your newsfeed, asking and answering questions and voting answers up or down.
There is a downside to the mobile edition, it's huge, over 800 KB for my homepage. While Quora works pretty well in the Android browser on a good connection, it's pretty slow to load on 2G compared to the mobile editions of Facebook or Twitter, for example. A page that large is unlikely to load at all in the embedded browsers found on many basic phones. I was unable to log into Quora at all using Opera Mini, the login page just reloaded when I pressed the submit button. That's unfortunate as Mini would be a good solution to using Quora on slow connections and basic phones.
Update: Quora recently started requiring invites again for non-US users, or maybe they always have. If you are non-US and need an invite leave a comment on this post requesting a Quora one. Be sure to put a valid email address in the email field (not in the body of the comment where spammers can see it).