One of the things that I love doing on the weekend is visiting my local SPCA. This is an activity that I definitely recommend to animal lovers who have a shelter near them. Check nationwide shelters like the ASPCA or the Humane Society. They sometimes have free weekend classes to educate people on how to raise puppies, so it's a good idea to participate if you're thinking of getting a dog sometime in the future. I just go to coo at them through the windows and sometimes play with the animals as well.
Furthermore, animals are known to reduce stress, so consider this a healthy activity that will help you take your mind off work and reduce stressors in your life. In fact, a certain ivy league law school even started using a therapy dog to test out the stress reduction theory on students. The dog will be placed in a private area of the Yale Law School library, and students will get the chance to interact with the dog only if they sign up for a time slot. Have your own doggy relaxation time by visiting the SPCA, and who knows, this can possibly lead to opportunities for volunteering at the shelter on the weekend.
Source: Flickr User mbostock