You can attach multiple PhotoPass cards to one PhotoPass online account. So what people do is arrange with other people going at the same time to attach all their cards to one account and then order the CD. Then, multiple copies of the CD are made and distributed to everyone who participated.
There are photo pass share threads on the budget board. Check them out, you could ask one of the organizers how they are doing it. I just joined one, but am not organizing it, so I might not be the best person to explain exactly how it is working.
Photopass offers a 20% discount if you pre-order their Photo CD for a total of $99. I haven't posted enough messages on this board yet and the forum won't allow me to post the link. If you are a frequent poster and want to post the link, send me a message and I'll share the link with you.