...the new Blogger bar at the top? it's a google search box for whichever blog you're on. Very handy, since Blogger doesn't let us categorize posts the way MT users do.
And, last night I just discovered All Consuming, which tracks mentions of books on blogs (if they're linked to amazon or B&N) and maintains lists of various sorts. Looks like you can sign up and have it generate a list of books you're currently reading for your blog, which is feature I've admired in several MT style blogs. (I love what I learn from occasionally looking at my referrer list).
Update: look down to the right... not only a list, but also lets you comment on them.