Every so often I get together with friends to do an informal gift "flash mob". We each suggest a charity and normally choose them all, then on a specific day every one of us gives a small amount. According to what we can afford. Together we can guarantee over £100 - and to small local charities that is significant.
More recently I have been doing this with friends in America, too.
We started doing this for Lent, but we are discussing it for Advent this year.
I also give to Lendwithcare.org. This is a charity set up to loan money to groups who would not be able to borrow from a bank [in what we used to call "third world" countries]. My choice is to give to women's co-operative ventures, but you could choose all sorts of groups. The group uses the money to buy more stock, etc., and repays the loan when it can. I have been getting repayments far sooner than I expected and I re-invest these with whatever extra money I can find.
I am NOT rich, but the joy it brings to give what I can is beyond description...