I have a 30gig video and the only thing I felt a need to buy for it was a case.
As for things I wouldn't mind having is the ipod dock, the ipod camera connector (use your ipod as a photo dump when you're traveling) , an fm transmitter and some random connection cords.
I use my Ipod every single day for at least a good 8 hours. I have yet to need anyting other than a case to protect it. I do have a good set of head phones I use. I have the Shure EC3's. While they might be pricey, they make me feel better about my long use time b/c I don't have to turn the volume up to hear my music. I have cheaper ear buds like the ones that come with the ipod, but I have to turn the volume up quite high to really hear the song and I worry about the high sound level hurting my hearing.
there's hope in the words and emotion in the eyes
it's so easy to be misled by the savvy gentle guise
and like fools we trust the delivery
but it's all just drunk sincerity