... please turn out the lights. This is my contribution to the Blog Azeroth shared topic of Jan 3-9, as suggested by The Casual Raider. I'd like to talk about what happens when your guild alliance collapses, which hopefully is close enough to the original topic idea.
So you have a small guild, not big enough to go raiding, but you'd like to. You form an alliance with another similar guild, where you do joint 10 man raids, and start seeing the content. Things go well for a while and you're all getting bosses down, getting loot and seeing the instances (ok just Karazhan actually). Then it becomes apparent that the aims of the two guilds, or worse the players in the guilds, are not the same. Your sister guild wants to do 25 man really and is getting impatient with your guild, who just wants to stick to 10 mans (death to the Prince!).
Finally it all falls apart and you are left with your sleepy guild, with raiding experience, epics and skills, but yet not enough people to put a 10 man roster together. This is what we did.
Decide your future
Back to running 5 mans? Or get into raiding? Your guild and its members need to decide how they want to play the game. Having gotten a taste for raiding, some members may want to skip off to a raiding guild. Others may not like the pressure and want to go back to 5 mans. If the guild decides to keep on raiding, tell everyone so they can decide what they want to do.
We decided to keep on grinding Karazhan because it was fun, and we had not cleared it, so we told everyone so. Nowadays there is an actual 10 man raid progression to look at, so even more incentive to carry on.
It is worth mentioning that you should try to be nice with the other guild. It may seem that you don't want anything to do with them at all, but some of their members may not be happy with how things went either. We parted on good terms with our allied guild, and later when they imploded (as a consequence of something else), we had one of their members join us.
Once the guild decides that it wants to raid, it's time to take stock and see who will stick around to raid with you, and who wants to go off somewhere else. Then it's time to see what classes and roles you have to actually do raiding. Luckily these days with dual spec there are likely to be some off-spec tanks or healers hanging around, or tanks who want to try DPS, etc.
We had to get a resto Druid to swap into tanking and just had enough healers to get going into Karazhan.
Get a calendar and Vent
If you were using the other guilds website to do sign ups, and/or their Vent server, you will really need your own. Luckily you can get a free guild website from the likes of Guild Portal or Guildomatic, which are usually restricted but good enough to plan some raids.
Vent is more problematic and we eventually borrowed another guild's vent and now have our own which a kind member funds.
With a new roster of raiders, some in different specs, we found it best to start again from the beginning, with little expectation of making the same sort of progress we had with our sister guild. This means people won't get so annoyed when you don't down boss x when you used to get him killed every week.
If you don't have the roster for raiding, but want to, get recruiting. This is quite tricky if you don't actually have a raiding schedule as people are more likely to apply if you are killing bosses, but having some raiding experience and epics might help attract people.
Go go go
Ultimately, the longer you leave it after a break up before you get raiding again, the more people get itchy feet and are hassling you to go raid. So we started raiding as soon as we could to see how far we got. Predictably we were set back a fair amount, but eventually we managed to push up to the Prince and clear Karazhan.
The other option for us was to call it quits on raiding and go back to how the guild was. The thing is, once people have a taste for raiding and the shiny epics, they don't tend to want to go back to running 5 mans, so the guild as it was no longer existed. The only way was to carry on raiding, or break the guild.
We changed into a raiding guild when our Burning Crusade raiding alliance ended, cleared Karazhan and started Wrath as a 10 man raiding guild. We managed to kill the Lich King and do some hard modes, and now are aiming at clearing the 10 man normal mode raids in Cataclysm. Had we gone back to just doing 5 mans, the guild would have likely died. Good luck!