Meta Keywords are no longer important in the major search engines, although some of the second and third tier search engines still use them.  Keywords in your title tags are quite important and the meta description is important when it comes to people actually clicking on your site in the SERP's.  If you want to learn more about SEO and Title and Meta tags, here are a couple of useful articles/sites that you can check out.

 Search Engine Ranking Factors

Intro to Internet Marketing

Here's a tutorial on Meta Tags and a brief mention of its value in the ranking factors.

Meta Tag Tutorial

As an SEO firm we use it to some extent. NOTE: Crafty SEO salespeople over-emphasize this as it sounds techy and makes SEO seem like it is complicated. So take any tags with a grain of salt, and worry about good keyword rich content and inbound links and you will do fine.