The best-known suit is probably Apple's against the "numerous unknown entities" who, Apple claims, divulged some of its trade secrets over the internet. The case is a mess and probably doesn't apply to your everyday blogger, so I won't get into it.
The Media Law Research Center (MLRC) has a handy-dandy page which includes the Apple case, but also describes a lot of other suits for libel and such against bloggers and websites. It's fascinating reading. (Sorry, no permalinks, but just scroll down to the state and you'll find the case). A few of the suits listed (many of which, somewhat unsurprisingly, concern alleged sexual defugalties):
Mississippi: A minister sued a former parishioner for claiming on her blog that they'd had an affair; Florida (Tucker Max again): "Plaintiff, formerly Miss Vermont and Miss Vermont U.S.A., sued over postings on the tuckermax.com blog in which the author recounted his alleged sexual exploits with her"; and Maine: The Gentle Wind Project v. Garvey, in which "The Gentle Wind Project, which describes itself as 'not-for-profit world healing organization with a remarkable healing technology,' sued critics who called the organization a cult."
Then there's Banks v. Millum (Georgia), "the first case against a blogger of which MLRC is aware that has gone to trial and resulted in a liability verdict." Interesting facts and figures:
If they don't hold bloggers themselves to a higher standard than anyone else (which Banks doesn't seem to do), I'll be happy.
Attorney Rafe Banks III sued political activist David Milum for statements made on his website on local politics in Forsyth County, Georgia, aboutforsyth.com. Several postings on the site alleged that Banks had delivered bribes from drug dealers to a now-deceased judge. After a four-day trial and six hours of deliberation, the jury awarded Banks $50,000 in compensatory damages, but no punitive damages.
Banks had sought between $400,000 and $2 million in damages. After the verdict, Milum said that someone else was taking over the web site. He also said that he may appeal.
(h/t: Dougie Houser)
Update: Now that I look, Glenn Reynolds has a paper on libel laws and blogs he posted last April (pdf). It's short and interesting (he draws particular attention to the fact that there are as yet very few suits against bloggers), but pretty general.