WikiAnswers is a popular but not as popular as Yahoo, Answers type site.  It’s a PR7 and shows up in google for a ton of great search terms very highly.  I found a little loophole a few months ago that gets you a link back to your site with anchor text, without having to even post an answer.

Warning: This is considered black hat and can get you banned from WikiAnswers.

First create a new account.  You might want to create several accounts depending on how many sites you’re going to be promoting.  Then have a look around for any questions that might relate to your niche.  Once you find a question, on the left side of your screen (the sidebar) you will find an option that says Add Related Links.  Click on it and where it says title add your anchor text.  Where it says URL add your site’s URL or affiliate link (preferably cloaked).  Click Add Link and you’re done.

Now you have a link on a PR7 website that gets tons of search engine traffic.  Remember if you’re going to do this a lot have tons of accounts and use proxies to keep what you’re doing subtle.  You’ll find a lot of your links will last a very long time.