We had a similar situation albeit with a different product, being poor people creating Ham and Jam and having spent months looking for someone to lend us a SVN server we were out of luck and rapidly running out of space on the graciously donated server by cvsdude.com
They said they'd happily give us the next level of service/server package but we'd have to pay for it. We were also due to renew our vBulletin licence as well as domain names. We spent a while trying to think of ways to pay for all this (probably about £150+) from splitting it between the team (£20 each or so) which we knew would be hard to sell, to having adverts which would be hard to stomach and then we just decided to have a donate button just to see if it worked. We expected nothing from it.
By pure chance/luck it turned out the devoted forum members we had were really devoted and we raised that money in about a week, we paid the bills and we've almost got enough for next years ones too. We also said come the time when there's nothing to spend it on, we'd donate it to WW2 Veterans charities too.