Google bought Aardvark last February and added it to Google Labs. It's a question-and-answer service along the lines of Yahoo! Answers and Otvety, but it works primarily via IM and email (though you can use it through the website as well).
Once you sign up, you add "topics" to your profile. Topics are subjects you know about, e.g. Google, cooking, spaghetti, Linux, and so forth. Aardvark uses them as part of its formula to determine whether it should send you a particular question.
Aardvark also looks at how you're connected to the asker; the more directly you know the asker, via Facebook/Twitter/etc. connections, the more likely it will be that Aardvark will send you that person's questions, even if the topic isn't listed in your profile.
When you ask a question, Aardvark uses its algorithms to find people most likely to be able to answer satisfactorily. You can converse with answerers and request additional answers if you're unsatisfied.