Instead of writing out a check and giving it to multi-million dollar groups like PETA or places where you really don't know how they are using your money when you give it to them, you can buy food, toys, and/or bedding and give them to your local animal shelters and while there if you can, spend some time with these animals by petting them and just showing them love as they are often times in shelters for so long they become anti-social thus harder to adopt. Try and help to keep them friendly and approachable. If someone is ill in the hospital and has a companion animal at home with no one to care for the animal, volunteer to take care of the companion animal, either by stopping by the house to care for them or taking the animal in until the person is released from the hospital (if you have that kind of trusting relationship with the person). Also, times are still tough for many people financially so if you know someone who is struggling to pay vet bills or struggling to feed their companion animals, you can help them pay for these needed things.
I have always stated the best way to be an animal activist is by being your own animal rights group--instead of paying other animal people/groups to directly take care of animals (do you really know how they are using your money?), start doing it yourself, and in this way you know where your money is going and you are really a part of seeing it help the animals.