Katie,
Welcome to Reef Central!
As the others have said, knowing what your goals are will make it easier to give specific advice. But since you've got a 30g tank you choices are a little limited. I'd recommend reading some books first to see if you'll be happy with a 30g before you start buying equipment. I've got a 37g and wish I had at least a 75g (or at least an Oceanic 58g).
The Conscientious Marine Aquarist by Bob Fenner is a great place to start. It's filtration section is a bit dated (today most people use a combintation of live rock and protien skimming, often with a sump and/or refugium, he covers this amoung others) but it's a great overall book.
The New Marine Aquarium, by Mike Paletta is another great introduction, and it has good stocking advice. You can get them together from Amazon for less than $40.
For a pocket guide to fish you can take with you when you go to the fish store, Scott Michael's Marine Fish is the way to go. Very handy for checking to see if that cute little fish will grow up to be a tank buster or will eat your corals. I've included links at the bottom of this post.
With a 30g I'm guessing you don't have a sump, which means you're limited to "hang on back" skimmers. The AquaC Remora and Remora Pro are probably the best out there. Once you've got a sump there are lots of options, but I'm not up on the best "bang for the buck" models. Euro-reef is great, but pricey.
MaxiJets are fine powerheads and perform great for the price. If money is no object and you want to keep high-flow corals withotu a sump or closed loop, look at Tunze.
Ebo-jager heaters aren't as sure a bet as they once were (company was bought out) but I'm hearing good things again. I have Finnex brand titanium heaters, which are nice (and unbreakable).
Finnex, CoraLife, and CurrentUSA have decent lighting options for a 30g tank (and other sizes). Metal halide lights are very bright and good for growing demanding corals, but they're very hot and rather expensive. T5 flourscent lights are good for all but the most demanding corals and clams (if you have enough bulbs). I have a combo MH and T4 light, a Sunlight Supply Maristar. Very nice, but very expensive. I'd probably go with the Finnex MH / T5 combo or CoralLife MH / compact flourscent if I did it again.
Premium Aquatics (
www.premiumaquatics.com) has very good customer service, dry-good prices, live rock (price and quality) and cleanup crews (price and quality). Marine Depot is also very good (
www.marinedepot.com).
You should also check out the Vendor Experinces forum and Lighting & Equipment formum on Reef Central.
While you're waiting for the books to come, check out
www.reefkeeping.com, an on-line magazine that's associated with RC.
Best of luck,
John
http://www.amazon.com/exec/obidos/tg/detail/-/1890087025?v=glance
http://www.amazon.com/gp/product/1890087521/002-1642569-8602463?v=glance&n=283155
http://www.amazon.com/exec/obidos/t...bs_b_2_1/002-1642569-8602463?v=glance&s=books