I just recently stumbled across this awesome site and I must say it's waay better then AnimePlanet. There a loads of things you can specify for your Animes, like rewatch value, watch priority, storage method etc.
But the best thing is, it features a program called MAL Updater that is basically like Last.FM just for Animes! Whenever you watch a Anime on your PC it will be added automatically to your list, episode for episode. It also has a season browser which tells you all upcomming Animes for fall 2009 for example and of course you can make dynamic signatures too (look at my sig^^)

Just give it a look and add me as a friend there if you want, my username is SkyDX^^