Stack Overflow is a community-driven website where you can ask any programming related questions and answer other people’s questions. Based on a good reputation system you start being restricted to only post questions and answers. By getting “up” votes on your posts you will gain reputation points and more permissions like voting other people’s posts and commenting them. With a rather large amount of reputation points you will even get moderator permissions for the platform.
Registration is quite easy. If you have any account supporting OpenID (such as Yahoo/Flickr) you will be able to login right away. Avatars are being loaded from Gravatar. Before asking questions you should try searching for earlier posts on that topic; one idea behind Stack Overflow is to build a large FAQ of programming questions. I’ve recently got Stack Overflow threads in Google search results as well (and in most cases they immediately solved my problem).
The speed of questions and answers is rather high paced. Many people are monitoring the list of newest questions and respond in about 3-30 minutes. It’s not uncommon to be overtaken while still writing on an answer – in these cases you will get a notification on top of the site which you can click to see the latest answers while still retaining your unsent answer. Voting is quick, too. But in almost any case quality matters and since there will be some extra points for accepted answers you are never wrong to submit your own one if it adds some new aspects, even to highly frequented threads.
It’s best to try it yourself but be warned: That site is addictive! :)