If there is an animal you are particularly passionate about you can find different programs where you can "adopt" an animal. The money will go towards helping restore that animals environment and encouraging reproduction. WorldWildLife.org is one that does that. You usually are rewarded with a fact sheet on your animal, a plush animal, and a certificate. You can even adopt a narwhal through them!
If there is an animal in your area that is endangered, find a preserve that houses them. For example, the Florida panther is endangered, but they have preserves you can go visit, which helps them expand their territory and reproduce.
Then of course just taking care of our environment.