One extremely useful site out there is Ask Metafilter. The premise is simple, someone askes a question and anyone in the metafilter community can answer.
Doesn’t sound too exciting but you find yourself getting answers to the questions you may have had you whole life but never thought of asking.
The questions can be ANYTHING. For example:
What’s better is that people can tag their question (much like Flickr) for easy searching. One of the things that motivated me to start this site was this thread about college productivity.
There is one downside: if you want to post or answer questions you need to pay $5 to register. But I dont think you need to pay the cash, just being a lurker is good enough.
And for a daily dose of random knowledge subscribe to thier feed.
[tags]ask metafilter, questions, rss, random knowledge[/tags]