Chris, this is one feature that never made it onto the xxD series... gay. I have a wired shutter release for the 10D and it's been a brilliant addition to the camera.... and £12 for the xxxD series (wireless too) is excellent value I think (depending on distance)
Bulb mode is ace... (put the camera in Manual mode to access bulb shutter mode)... basically 'Bulb' mean you dictate how long the shutter remains open for... It
can be operated through shutter presses on the camera, but you have to hold down the camera for duration of the shutter actuation which means you'll likely shake the camera, ruining the shot.
These two were taken using bulb mode (shutter time was +8 mins for each). basically I pushed the button down, went to grab a chocolate bar, stood around and bit and messed around with the mobile phone and then depressed the button when I got too bored.
It gives you a lot of flexibility especially if you're going for long exposures shots on a tripod... even the shutter itself will stop the picture being pin sharp so use the Mirror Lock Up function too (see your manual
)
Any q's then fireaway man