My favorite things are:
LibraryThing because I will use it to keep track of the books tha I have read.
BlogLines because I can find blogs to read regarding issues of concern to me.
Podcast.com because I can listen to radio broadcasts that air I when I'm unavailable to listen.
My least favorite was when the websites had technical difficulties --Odeo and Flickr. This was especailly true for Flickr because it was an exercise that we had to do almost at the beginng. I can see where the problems with Flickr could have discouraged many staff members from continuing with the other exercises.