I just started using this neat little app called CoverSutra today as a supplement to my music listening experience on my computer. What CoverSutra does is add additional iTunes functionality without the need to keep switching back to the iTunes application. CoverSutra adds a small music icon to the menu bar and from there you have the ability to search and pick individual songs using keyboard shortcuts. In the end, the song-switching and song-picking procedure is sped up a lot because you don’t have to mess with the task switcher or move your cursor to select iTunes. It doesn’t sound like much when I’m explaining it in words, but CoverSutra is so good at saving me time to be better off spent elsewhere that now I can’t ever see myself turning it off.
You can use the link provided above to try it out.

I use quiksilver with the itunes plugin.