It is a good idea to know what you need before you go. Pet store employees will try to sell you a bunch of crap you don't need and that can be bad for bunnies. Most of them don't know much about cats or dogs let alone rabbit and other 'exotic' pets.
Cage: The bigger the better. One thing to keep in mind is that most companies measure at the largest part and the actual floor space is much smaller. For what you spend, a large wire dog crate or an x-pen is bigger and more suitable for rabbits. Also look into NIC (C&C) cages. They are much cheaper than most cages and you can make it as big as you want or have space for.
Bedding: If you litter train, you do not need litter in the while cage. I use wood pellets in the litter boxes and have fleece blankets in the rest of the cage. Be careful about materials that you use as some rabbit like to chew them and you don't want stuff that has string and threads that can be ingested. Towels can be bad for this. I would get at least 1 more blanket than you need for the cage so you have something while you do the laundry.
Litter box: As cute as they are, try to avoid the small corner boxes. They tend to not be big enough for most breeds. You might get away with one for a lionhead, but it would not work if you have a bonded pair. I use large size cat ones. It can also be a good idea to have a grate over the box. There are some that come with a grate, bu you can also make one using wire mesh, a florescent lighting grid or plastic stitching screens (at craft stores). Also get a cat litter scoop or something to make cleaning a bit easier (go to a dollar store for this).
Litter: Wood or paper pellets are best. Petsmart does have a house brand of both, but the wood pellets are kinda expensive. If there are feed stores near you, check them for Horse Stall Bedding. Hardware stores should carry Wood Stove Pellets at this time of year.
Dishes: I prefer dishes for both food and water. Petsmart has metal dishes than clamp onto the cage in the bird section that are suitable for rabbits. I do like the ones that clamp on rather than the ones that just hook on as the ones that hook on can still be thrown around by a determined rabbit. If you do use a bottle, get one that is about 16oz so you don't have to fill it all the time. For a food dish, get a ceramic ones. Plastic can be chewed which can lead to bacteria getting into it.
Food: Proper diet is very important. You will need pellets and hay from the store. For pellets, get a plain pellet and avoid the mixes. I believe that Petsmart does have Oxbow pellets. For young rabbits, get an alfalfa pellet, but for adults (6 months and over) go for a timothy based pellet. For hay, young rabbits should have alfalfa while adults should have grass hay like timothy. Buy the biggest bag you can find (and afford) as you will use it all. Another good option for hay is to buy it in a bale. If you might have trouble storing one, see if there is someone near you who will share one. I can get a bale for $10 while a bag that is 5 pounds also costs $10.
When you get your rabbit, get some pellets from where you get it so you can slowly switch the rabbit over.
Toys: Rabbits need toys to play with. A bored rabbit is a destructive rabbit. For pet store toys, get grass mats, things to toss, balls with bells (try the cat section), a hay ball (wire basket that you can stuff hay into) and maybe some wood blocks (avoid colours). You can also use paper towel tubes and stuff them with hay as a toy. Cardboard boxes and cat tunnels (or cardboard ones if you can find them) are also good.
Cleaning: For cleaning I use a cat litter scoop, dust pan and brush and a spray bottle that has water and while vinegar. You don't need special cleaners. You can get this stuff at a dollar store and just use regular while vinegar. I use the litter scoop in the litter boxes. The dust pan and brush are for sweeping up poops and hay in the cage and the water/vinegar is to spray down the cage and clean up any pee spots. Vinegar is also good to remove urine stains in the litter box, just spray is and let is sit for a few minutes and give a bit of a scrub before rinsing.
