I am going to be running with nearly 10 players. We had 10 for a test run last night. It seems to me that 10 players makes it very difficult to do much role playing because most everyone would have to shut up and wait for long periods of time. Are there some setting that work better with large groups? Maybe some sort of military campaign with lots of battles? I am at a total loss about what could work best, but I don't want to throw in the towel without at least giving it a real shot.
If you're OK with not having everyone around for every session (and especially if you feel a desire to place limits on how many players can be in a given session), then a West Marches-style campaign is designed in a way which specifically addresses this issue::
2) There was no regular party: each game had different players drawn from a pool of around 10-14 people.
The basic idea is to have a single "home base" location (in the case of the original West Marches, it was the last outpost of civilization prior to reaching the frontier that the PCs spent their time exploring) and arrange things so that the PCs return to their home base by the end of each session. This allows the freedom for the group of characters present to change completely from one session to the next, since they're all in the same place between sessions. This would also work well with an urban campaign in which the PCs never leave the campaign city.
This style of game seems to work best for sandbox-style exploration, since that avoids problems with ongoing (GM-prepared) storylines that can be broken (or at least complicated) by characters disappearing in the middle of them.