Samurai Champloo is a bit of a rollercoaster.
Varies in quality quite a lot. Loved the fight scene in the rain with the blind girl.
Dunno why they changed the style so drastically for it though... it looked much nicer before.

The Cowboy Bebop series is a bit lacking at times as well, but there are a few gems in there.
Last couple of episodes were brilliant, as was the 1st and 3rd (I think), but there were a lot of unecessary episodes that featured ridiculous plots too.

The animation in Mezzo Forte is quite nice too:
http://www.youtube.com/watch?v=y8wum1C5b9w
It's completely over the top though; much like a kung-fu movie. Might be a turn off, might not.
They also made a series entitled Mezzo that features the same characters, and has pretty nice animation up until the midway point at which it went down the toilet for reasons unknown to me.

I believe Kite is similarly well animated (made by the same guy) but has a better plot. Haven't seen it though, so can't verify.

Miyazaki's movies are always fun, although I think his plots are becoming too abstract.