DIY remote cable for Sony DSLR A100 (and others)
Essentially the remote release cable consists of an on/off switch assembled into a film canister, and a cable from a CD-ROM drive. I only made the cable for bulb exposures (the A100 has mirror lock-up when using the two second self-timer, so I usually just go with that for stability), so I didn't bother with a button-type switch. The cable is just the audio cable from a CD-ROM drive–by lucky coincidence it fits into the remote release port on the camera. No other components necessary. The whole operation took about 20 minutes.
(Maybe it's not that pretty, but see how much the official cable costs. ;>)
See the next photo for the pin layout of the remote port.
See this post for details and conversation on how to do it yourself.
The cable should work with all Sony and Minolta DSLRs. The same principle applies to at least some Canon and Pentax DSLRs, but you need to replace the CD-ROM audio cable with a 2.5mm miniplug (I think), and google the pinout (see comments below for one link). For Nikon you also need some diodes.