When looking to stay at Disney you'll see a few diferent classifications of Resorts. Aside from the cost, you may be wondering what exactly the difference is. Largely the difference is size of the room and the various amneities available at the resort. By and large nearly all of them will have a fridge, a small table/desk, a television along with bed(s) and a bathtub with a shower. All of the Resorts have a pool and somewhere to get some food, as well as bus stops to the Parks and Downtown Disney.
The affordable bunch of resorts consisting of Pop Century, Art of Animation, All-Star Music, All-Star Movies, an All-Star Sports. Excluding the suites, these are closer in to your regular hotel room with Disney theming. They are typicall smaller than the other resort types and usually only have double beds or a queen size bed. With dining you have quick service and pizza delivery, but no table service on site. You can of course go to another resort or park for that. Lastly, their bus stops are typically located the furtherest from the main entrance with the exception of some of the non Downtown Disney area resorts that are not operated by Disney but with bus transportation to the parks (usually operated by Mears). The theming which is impressive is generally at an over the top level around the resort. Really thee are best if all you really want is a place to bath and sleep, or if you know you wont use all the extras of the higher levels and want to save some money. I've yet to stay at Art of Animation, but I've walked over from Pop Century to look around (there is a connecting bridge). It is absolutely gorgeous and like Pop, has it's own buses. Personally I'd stay at one of those two because of that, they they are a bit more expensive. These run $90ish to $130 a night.
Averaging about 70 bucks or more a night ore than the Value Resort, the moderates add in some resort amneities and are a bit larger. They typically have 2 queens or 1 king sized bed, quick service and usually access to an on site table service location. Their bus stops are closer than values, some actually land you closer than some of the Deluxes. In general they tend to be a great middle ground between breaking the bank and getting some perks. The theming takes on a more subtle style and gives each resort a special feel, which also carries over into the Deluxe types. Starting with the moderates you also start seeing lounges and some recreation activities besides a pool and arcae at the resort. Some have fitness centers or trails, some have fishing, etc. For the most bang for your buck I'd recommend Port Orleans, specifically the French Quarter. It is smaller, beautifully themed, and right in the middle of Walt Disney World making it a short ride to get to anywhere. These tend to run $120ish to $300ish a night for a regular room.
The deluxe resorts are the cream of the crop, having several recreation activities available and some with on site spas. They have one or more table service locations, a quick service location and often have either boat or monorail transportation to one of the parks, though some of them do not. The theming here is absolutely amazing and breathtaking. These are the places you go to be awed, pampered, and just sit back and relax. Many are also DVC (Disney Vacation Club) Resorts and have extra perks for DVC members, some only being offered if you are there staying on points. For instance, The Animal Kingdom Lodge has it's own savannah you can view the animals on, The Polynessian can see Wishes from the beach, The Boardwalk and other Epcot Area Resorts can enter right at World Showcase. Personally, as an animal lover, I would say staying at the Animal Kingdom Lodge with a Savanah View should be something everyone experiences at least once. And while you're in the area, go eat at Sanaa at the Kidani Village. These can run in the $300 ballpark upto $700 (or more) a night.
The Deluxe Villas are really an off-shoot of the Deluxe Resorts. They have all the goodies of the Deluxes but are designed for larger parties to stay at. As such they are also typically the most expensive places to stay at on Disney Property.
This chart below from TouringPlans.com will give you an idea of the square footage the resorts have.
This is a somewhat unofficial category, however, The campsites of Fort Wilderness don't exactly fit in with the other classifications in my opinion. Fort Wilderness is the only Resort that you may bring your pet with you. The campgrounds are also typically the cheapest place to stay on property. Along with Ft. Wilderness, there is also Best Friends Pet Care, a resort for your pets (aka a fancy kennel). It offers both daycare service and overnight accomidations for your pet, baring some exotic or venomous types. It's right across from Port Orleans. Dogs and Cats can get accomidations while the rest must have their own enclosures. The size of the enclosure determines the rate. Note: you must have up-to-date documentation of vaccinations, etc.