Someone just sent me a link to WorldVitalRecords because they have free databases until 11/30/2009. I liked it. I have a subscription to Ancestry so I'm not sure if I need another one. I'll have to browse more and see what all it has to offer. Look for the banners for some of my favorites, on the left side bottom. I think some ads automatically show below my blogs too.
Here's some more: Ancestry, myheritage, LDS, Footnote, familyrelatives, newspaperarchive, familytreemaker, rootsweb, familylink, legacy, findmypast, surnameweb, Intelius, cemeteryspot, mygreatbigfamily, genforum, gencircles, familytreedna and rootsweb. (of course put www. in front and .com behind the word)