SEO tips for bloggers

Just learned a ton about SEO in a short time by attending a video conference for International Freelancer's Day.  I can see I've got a ways to go since I'm not quite a corporate blog writer.  I'm not going to rehash the seminar -- you can find a lot better tips on SEO and keyword research in a million more places - I am really liking Copyblogger (Brian Clark did the presentation).  I'm pretty sure the presentation is archived there, or just download the materials from Copyblogger.

Not sure if I'm ready to jump into a subscription to a keyword research service yet, but maybe my company will for its blog.   This could be a cool experiment.

Does anyone have a keyword research service they like?  Any free ones you can just try out?