I love my iPod [1].
I don't really use it for music, I mainly listen to podcasts.
I guess that 90-95% of my iPods[2] playtime has been spent playing podcasts[3].

I spend 45min on the bus to and from work. Listening to podcasts transforms that time from wasted to well used.
A pair of good noise isolating earphones allows me to ignore the brats that sometimes crowd the bus. And when flying they keep the engine noise out.

The podcasts I like are mainly about science and technology.
Loosely sorted by quality, they are:
Radiolab
Quirks & Quarks
BSDtalk
So Ein Ding (In Danish)
Harddisken (In Danish)
The Naked Scientists
Videnskabens Verden (In Danish)
Ask Mr. DNS
IT Conversations (Quality of the shows varies wildly)

Other podcasts that I like are (in alplabetic order):
Dan Carlin's Hardcore History
Danmark Kort (In Danish)
In Our Time
Pat Condell's Godless Comedy
Selvsving (In Danish)
Tjenesten (In Danish)

[1] And I know that the RMS fanboyz will hate my guts for that statement.
The fact is, that for my needs, an iPod beats the competition hands down.
[2] Some asshat stole my first one.
[3] Yes podcasts. Not pirated copies of music made by mediocre "artists", whose only claim to fame is what their label bought them. Eat shit IFPI.