I tend to buy a few gifts from Oxfam each year (a goat, a set of school books, that sort of thing), and give a small donation to Shelter each Christmas (note, must do that). And the occasional one off, like the recent Cyclone DEC appeal.
Also, I do a lot of shopping in charity shops, so they all benefit from my meagre spendings....
When I'm settled in a job and have a reliable income, I'd quite like to sponsor a child, but money's a bit tight to be making a commitment at the moment.
Oh, and of course, I ask any recipient of a knitted beastie to bung a couple of quid to Oxfam or something else... And I've got a small stack of knitted vests and bears to send off to a charity in South Africa... (Further note to self - get them sent!)