Yes, they work fine on most flashes. I had tape on mine as sb600s don't play too happily with them, and 430ex users have problems as they seem to with every hot shoe thing.
Ordered some more to put in a headphone jack as cheap and reliable sb600 hot shoe adapters for hooking up to modded trigger recievers. Put some tape over the sensor and they're just an adapter, take the tape off and you've got a backup triggering solution.
http://www.dealextreme.com/details.dx/sku.8201 wee bit cheaper and with some comments here, though linkdelight's dispatch will probably be slightly faster. They also do ones with a pc socket in the side.
Don't forget to put your built in / on camera flash into manual mode, or the TTL preflashes will set this off and the actual exposure will miss the flash.