I still have way too many Wordpress plugins running, but seem to keep adding more.
The latest ones I like very well are
RSS Signature and one to
add related posts to your feed.
They're part of my efforts to ensure that if any of my full feed posts get swiped by the automatic harvesters that stop by now and then, at least I'll get some backlinks out of the deal and readers will know where to go for more posts.
Beyond that, Akismet is invaluable, especially now that I've enabled DoFollow and the automatic commenting programs have started to find my blog.
Jay