I got my hands on an old motherboard and case. The mobo is an ASUS A8NVM CSM and the case is an old Dell 3000. I managed to get everything wired up except for the front panel audio (which I've practically given up on) and the case speaker. I can't find anywhere if the case speaker connector pinout is the same as the standard case speaker, and I'd prefer to use the case speaker instead of try to get my hands on a new speaker. Does anyone have any idea about whether or not the connector will work, or anyone know the pinout for it?
I installed a third-party motherboard (ASRock AM3+ with quad-core Deneb CPU) in a Dimension 3000 case, but didn't come across a case speaker. I did rewire the front panel audio for a standard Molex 2x5 connector, though; the pin assignments are Soundblaster and that has been documented.
Somewhere, I have a picture of the front panel audio pin assignments, but if you search online, you should be able to find it yourself.
I've heard some cases don't have speakers. Mine was next to the floppy drive, directly to the right looking at it from the front.
BTW all the pictures I've found have been moved or removed because the threads are old, most recent one is Jan. 2012.
There's a picture here.
The "fun" part of doing this was the crimping; I used pairs for pliers for the task, one sourced from eBay ($10 or so) and the other from DigiKey ($65). The first was for the strain reliefs, and the second was for the actual B-crimps. If you're handy with solder, the second crimper can be avoided.
Soundblaster-to-PC front panel cable. This has a female SoundBlaster connector, but you can see the pin connections.