I do some SEO on each site...but nothing researched. I come up with key words for each site, and work them into the metatags and text. My small niche sites end up with Google PR's from 1 thru 3, so only the less popular keywords (ie., microniche) seem to get hits.

These days I submit the small sites only to Google and Yahoo search engines (and, of course, a hell of a lot of link lists and a few top lists!)