Strange Horizons is one of the awesomest genre magazines around today. They publish great fiction, they have an editorial vision and philosophy that appeal to me as a reader and a writer, and they make it all happen with donations from the community.
I think you should donate! The money you give supports fiction, non-fiction, and a group of editors who strongly believe in presenting a diversity of voices in the genre.
You can donate any amount you want, but if you’re the type who enjoys getting stuff at different membership levels, SH has that, too. $25 will get you a membership card (designed by Jeremy Tolbert, who is awesome), $50, $100, $250, and $500 will get you other, cooler stuff. Go check it out.