I think herein lies the issue with nominating a single charity - everyone has differing opinions about what their preference is/what they feel most inclined to give money to.
So far, it seems that the air ambulance and children's cancer are the two that are proving the most 'popular'. So how about we create a thread with a vote option for either of these two? The most-voted charity is the one we donate to over the course of a year, then after 12 months we do the same again - perhaps nominate two more, and go the same route?
We create the vote thread, leave it open for say a month to give everyone the chance to chip in.
I also think that Syer's suggestion of making donations through the various options he listed above is the best way to do this. if people wish to donate more/on a regular basis, that is their prerogative. The idea is, that whenever we have a meet/big event etc, there is the motivation to do it for a good cause too.
From the point of view of the collecting of the funds, we would also need to decide if donations are made by the individual directly to the charity, or whether we have a forum member be the 'treasurer' who would collect the money centrally, then pass over to the charity at the end of the 12 months.
C&C's please dudes!