Adam Pash over at lifehacker has a great post up on managing your iPod without iTunes. The post focuses on cross-platform tools for adding music and video to your iPod from practically any computer, the most interesting of which is Floola. Floola has a bunch of features, allowing you to copy music (in both directions), manage playlists, podcasts, etc. Best of all, Floola can be installed on your iPod (you must enable disk usage to run Floola), so you can run it on any computer you happen to have access to (including, if you are rather unfortunate, a Windows PC) directly from the iPod. In addition to Floola, Adam also mentions running myPodder, again directly from your iPod, to manage your podcast subscriptions, as well as some Windows specific tools. I'm not quite ready to give up iTunes just yet, but if you carry an iPod back and forth between two computers, as I do, Adam definitely has some good suggestions.
Floola is a free download, but donations are requested. myPodder is also a free download, but you must register with podcastready in order to use it.