I try to posts in forums a lot to promote my website by using a signature that has my site link. This is probably a dumb question but isn't that sort of like a link pointing to my website from that website? Does it help in ranking at all to have your link seen by the spiders in a high profile site such as IVillage message boards?

Well, it's likely going to depend on the value of the individual page. You'll often find that a forum's dynamic pages have low 'value'. There are many reasons for this; however, this does not mean that all forum posts have a low worth as deemed by a search engine.

Nonetheless, it's all worthwhile putting a link in your signature, yet don't expect to see an overnight sensational ranking in your favorite search engine.

Don't expect much if any SEO benefit. Links in forums, any forums, are so weak they're virtually worthless. If you are going to participate in forums for the sake of promoting your website forget about the SEO value (as there is none) and do it because people actually visit the websites in people's signatures. So make quality posts and you will see the benefit of forum signatures.

The benefit of adding Links or signature in forum is to promote your site by sharing your opinions about specific topic, getting more quality backlinks, reciprocal links and advertising your site.