Welcome, Rebekah! This is indeed a fabulous resource, one from which I have learned and continue to learn immensely.
Congratulations on mastering mozarella --
not an easy cheese at all, despite the reputation of the 30-minute variety. As for your next cheese ... what do you like? If you want to try a hard cheese, and like something in the mild-cheddar range, let me suggest a Lancashire or a Caerphilly -- search the forum for recipes. Both of these are ready in a relatively short time, allowing you to get faster feedback on your efforts. As for equipment, here's the basic list I think would be needed to make hard cheeses; search the forum for a variety of options on all of these:
1) Appropriate size of stainless pot or pan -- or possibly two, one slightly larger to make a water bath for the other
2) Miniature measuring spoons (1/8, 1/16, 1/32 tsp)
3) Cheese ladle or other spoon/spatula for gentle stirring
4) At least one decent-quality thermometer -- I like the dial type, available for around $10-15. Buy two if you plan to use a water bath -- it makes it much easier to hit temps.
5) Curd knife -- I just use a large cake decorating spatula
6) Cheese cloth -- I prefer butter muslin
7) Stainless colander -- don't use aluminum!!
Cheese mold -- can be re-purposed plastic container with holes drilled
9) Cheese press -- again, search the forum for countless examples ranging from dirt-simple to complex, just about any of which will work just fine.
I'm probably forgetting something ... oh yes: optional for cheese-making, but a virtual necessity for participation in this forum: a digital camera to report on the results.