YAY something I know a lot about
I would have to say iPod
especially iPod Touch as you can also load video, get some very cool extra add on's apps via the App Store
if you want to go all out get the iPhone ( wait though new model being might be announced soon
the interface is very simple to use
my self I have the iPhone 3G and find it soo easy to use,
if it is just for Podcasts, and Music, then look at the iPod Nano, as it has a screen to work out what you are listing too and will do exactly what you want.