Android phones, apps and tablets

Not sure if it works the same, but on the G1 there is an extra step. You have to select to mount the phone when you plug in the USB. There is a pull down at the top of the phone screen once you plug in.
I use a mac and found a great app that lets you sync with iTunes / iPhoto etc automatically. Am working away from home but will post it when I get back.

You have to do that on PC too.

When you plug it in you need to mount it.

There's also a setting in the menus somewhere about "USB mass storage only" or some bollocks that might need changing.