I definitely go through phases.

I actually rarely listen to music on my PC nowadays. If I do, it's through some sort of online radio, like Pandora, or Shoutcast (in itunes).

I mostly listen to my iPod (thanks guys!!).

But sometimes I'll switch to listening to music from my PC and get stuck doing that for a while. And if that happens, it's a toss up between Winamp and iTunes.