When I was a Windows user I stumbled across Democracy Player (now Miro) the program is just a video program that supports almost all video formats you can think of. I downloaded and installed it but at the time was unimpressed. I'm still however on their mailing list and now that the program is 1.1 I thought I'd give a another shot.
Installation seems easier on Ubuntu that it was on Vista, just a case of adding a repository and searching for the name of the program. (I love synaptic!)
The program then asked me where to search for media, I picked my Vista hard drive because thats where all my media is. Then after sorting through the files it could and couldn't play (when the program can't play a file it offers to play it through an external program instead) and the ones I didn't want cluttering up my playlist (like the raw footage from my YouTube videos) I started looking at the programs most impressive feature...
Internet TV, in a few clicks I had downloaded the latest episode of Spriggs (A Halo 3 machinima) from YouTube thats something you can' t do natively with YouTube!
Another great feature is Miro Guide which is basically video podcasting, within 3 minutes I'm subscribed to Cnet TV's Buzz Report just like in iTunes on Vista (But with fewer bugs!)
Linux is probably not going to get a all in one replacement for iTunes any time soon, but for all your video podcasting needs Miro is a brilliant program. I'm one step closer to ditching Windows for good!
P.S. Sorry about the stupid screenshot window in the pics obviously theres a timer function for a reason!