Out of curiousity what are some companies that sell land for development?

Real Estate agents, usually, also the cities themselves. Up the street from me there is a 500 acre area for sale, about 150,000. Pretty good deal, except the fact that it's a giant swamp. It's being sold by a real estate agent. In another case, our city is growing (by -3 people a day, but they're still building houses..) every once in a while, the city goes out, makes roads, and sells the area to a private devloper, who builds some houses, and sells some plots of land for development by individuals. When they are made by the private developer, they are just the same 5 or 6 plans, mixed a bit. Every once in a while, there will be two of the same plan beside each other :p

Some agents (http://www.privateislandsonline.com/) even have whole islands for sale :)