Yes you will get a backlink. But keep in mind most of these backlinks have the nofollow tag and thus not increasing your PR / rankings. Search around here on DP and you will find a nice list of blog that "DO FOLLOW"
ah ok thanks! But what happens if I post like on 2-3 blog post. It doesnt mean I will have 3 back links do I?
Yes, that would be 2-3 backlinks. You may find this useful as well: Forums that DO FOLLOW signature links: http://www.swollenpickles.com/2007/07/17/list-of-forums-that-allow-dofollow-signature-links/ Good luck!