I am using a few plugins: the
Broken Link Checker and the
Dashboard Widget Manager. (The latter let's you clear stuff you don't want to look at out of the admin dashboard.)
I had a
stats plugin running, but I think it's incompatible with WP 2.5.1 -- at least, SOMETHING took my blog down today and from the error logs at my host it's looking like this was the culprit.