Almost every time I give money to somewhere I regret it.
We made our donations last year, nothing major, but our biggest was a whopping $400 to Heifer. They've called me no less than 5 times since then, and sent probably 5 or 6 mailers.
I keep telling them, I'll probably donate again at the end of the year, when there's a big match, please stop.
I gave like $25 to my university many years ago when I first graduated. They still bother me constantly.