we got ours from Argos they were pack of 9 wedding cameras (needed 2 packs though, i have since seen them in the ASDA superstores aswell not sure on price of those ones though) we paid £49.00 for them with free developing (just had to pay £1 p&p)and they were deffinatly one of the best things we done.
There was a card supplied with each camera which explained to people how to use them and to hand to the best man at the end of the night, but just to make sure people knew our best man brought it up in the speach and we did get them all back .
What was nice aswell was the majority of the tables took sensible photos of each other before the wine started flowing so we had some really decent ones from the day time and some really funny ones when everyone was drunk, they deffinatly captured bits of the day which you cant remember i remember when we got ours back saying OMG did i do that ! etc .....

as there are shots which are taken and you have no idea at the time !
well worth every penny i say even if you do get the odd crap ones which had no flash used.
love
claire
xx