What are the best ways for me to help cats if I am unable to adopt more? I'm already at four, which, given my apartment size and resources, is about my max but I'd still like to help cats in need.
Great that you realize your limits but still want to help! Look up your neighbourhood shelter and decide how you can help out. It could be donating funds or being more hands-on, like volunteering time, either with smaller rescue groups or city shelters, or working with organizations dealing with feral cat colonies and spay/neuter/release programs. Volunteering can be as simple as going by to spend time with the animals and giving them some love, or more involved, like transporting cats to vet visits and helping out with cleaning. Spring/summer is always bottle-feeding baby time and volunteers are needed around the clock to bottle feed the tiny kittens. If you decide to work with a feral colony charity, you may help out on the streets, trapping ferals and making sure they get spayed/neutered, giving them a temporary home (such as a bathroom in your apartment!) to recover in before they are released into a feral colony. Most of the ways to help will require a short introduction and learning period with the shelter, so you can learn how to best lend a hand (and also so they know they can trust you). You can also meet some really great people this way too!