|I am quite a big fan of the Sims 2 music, particularly the build/buy mode songs and the Neighbourhood music. Mark Mothersbaugh is the composer of this music. There was even a full press release about this. Find it here: Press release.
Now if you would like to listen to this music outside the game aswell, there are 2 things you can do.
The first thing is to Copy the .package files from C:/Program Files/EA Games/The Sims 2*/TSdata/Res/
*For the music from the expansions, replace 'The Sims 2' with an expansionpack name.
Just copy it to an empty folder or your desktop. Now rename the file extension to .mp3. so for example if you have Buy.package, rename it to Buy.mp3
The only drawback of this is that all the music is in one big file. Did you know that The Sims 2 music is also available on I-Tunes? Currently the music from The Sims 2, University and Nightlife can be found there. The price is about $10,-- an album. I bought all 3 and really recommend them. Note that it does not include music from the Sims radiostations. You can find Mark Mothersbaugh's music here: Sims 2 music
Maxis audio director Robi Kauker is in charge of the radiostations; The rap, salsa, heavy metal, pop songs and more. Gamespot posted a big article on him here: Gamespot Simlish stylist Robi Kauker
It is certainly possible to put your own MP3's on the radiostations. To use your own mp3's, you need to copy the mp3 file to: My Documents\EA Games\The Sims 2\Music\[subfolder]\