Once, when I was younger (28 or so), I went to a meeting of the Jewish Business and Professional Women of Greater Phoenix. I had gone mostly to their evening networking things and this was a brunch with a well known speaker, a woman who survived the Holocaust. Yes, you can see what was coming. After the food and speech, they started with the "give to the campaign." I was not only shocked, albeit a bit naive, but then my shock turned to disgust. I actually said something, like, "No I'm not giving. I came hear to hear the speaker and meet people. I don't really care that the $ is going to... I give money to my synagogue..." Wow, that was the kiss of death. I really didn't know about this stuff, and I think they gave me a little leeway, as I was 8 months pregnant. Using the speaker's experience as a guilt trip to give really pissed me off.
I do give money to just a couple of things, but I always regret it, because of the incessant calls and stuff.