Getting your link published anywhere that isn’t a spam site can help you in most places. Yahoo! Answers isn’t really the best place for this because the address of your site itself will be linked rather than key words, which are pretty important with Google. If the links aren’t a source for the answer you provide, including them in your answers could also be considered spamming and get all of your answers removed.

If a link to your site is approved (well, not deleted) by Wikipedia, that will help your page rank as well as having your site linked in other forums. However, you should check Google first and see how well these other forums are ranked. If they’re not ranked well, it probably won’t do much for your own ranking. The thing to do is to have a good enough site that the websites Google already likes are willing to link to you. Content is the key.

Good luck!