iTunes. iTunes is my savior. At home, I have a library exceeding 25 gigs. I have to sort through and do some culling; the herd grows excessive.
At work, I bring my boyfriend's laptop and use it as an overgrown iPod. There are only 9.5 GB of mp3 and that other format Apple's using for music files on that machine. (.aac? They sound darn good, whatever they are.)
The music on my two machines is quite diverse. I listen to the work one so much that I've developed an obsessive habit about the play stats. I like best sorting the whole giant library by play count and then listening from the songs with a count of 0 up to the higher ones. At this point, I can't get through the whole playlist in a day, or two, or even three. So pretty much throughout the week I work through from the bottom to the top, skipping the ones that don't need to be advanced (you can uncheck them and they won't be played)... and then when i need to think about something besides work I look at the distribution, because i don't understand numbers at all but I kind of like them. :D
The one at home is a brand new computer so I haven't had time to accumulate any stats. I have trouble listening to it because I don't know where to start!
The actual music contained therein is all my CDs, all my boyfriend's CDs, all the CDs i've ever borrowed, and all the mp3s I've ever begged, borrowed, or stolen. My favorite songs are mixed. I have the 4-disc B. B. King set in there, so he comes up often... I like Susan Tedeschi as well, and just recently got a copy of the Stevie Ray Vaughan box set. That's all my boyfriend's music. Good blues stuff.
I listen to a lot of blues and jazz, a lot of what's loosely defined as "folk" (Indigo Girls, Joni Mitchell, Ani DiFranco), a lot of what's tightly defined as "folk" (The Chieftains and some other traditional Irish bands, as well as Gillian Welch and the O Brother Where Art Thou soundtrack), a fair bit of just plain "rock" and even some "pop" and maybe some "punk" if you can call it that (Bare Naked Ladies, Tori Amos, Nirvana, Manic Street Preachers, Dropkick Murphys, Motorhead), and yes, even some trance I inherited from an ex-boyfriend's mp3 collection. (He loved Orbital. I have a lot of Orbital. it's good when I don't want to pay too much attention but just want to get my groove on.) Man, I'll even listen to country if it's good. (I have more Steve Earle than I strictly intended to. And Townes Van Zandt. And what genre is Roger Cline and the Peacemakers? I've never been quite sure.)
I can't work without music. Music helps me focus. It's absolutely invaluable. I can't listen to one particular thing for too long, usually, which is why my playcount "playlist" is so perfect-- it's songs I like, sort of in the order I like them, not sorted by artist or genre or album. So... I love iTunes and wish I could afford an iPod so i could have it with me all the time. Heck, if it were waterproof I'd take it in the shower with me. In fact, if they could make the headphones wireless and implant them directly into my skull, that'd simplify things a lot too.