Satelitte dish tv/internet/phone
Let me add a little to what John said.
Cell phones have become the answer for phone service. They are reasonably priced and can be used in most locations. The two leading providers are Cingular and Verison. Which is best depends to some degree on where you go, but is mostly just opinion.
On TV, a great deal depends upon just how much you want to watch and how important is it? We tend to spend a lot of time in remote areas and my wife does like her TV so we finally broke down and got a dish. The cost is exactly the same as for a house and you can get the dish mounted on a tripod that you can carry with you. Have the installer show you how to point it and with very little practice you will find it pretty easy to use. If you stay near the cities you won't need it, but in remote areas it is the only way to have quality TV. There is also a special waiver for RVers that will allow you to get the network programing from one of the major city TV markets too.
For the internet, the best choice again depends to a great deal upon where you plan to spend your time. As a fulltimer you will probably quickly find that a telephone ISP is just not a good choice. WiFi is the least expensive, generally but it is also the least available. RV parks are putting it in very rapidly, but there are still no more than 1/4 of the parks that have it and less in the more outlying areas. Very often you will have to take the computer in the car to go and find a place where it is available. When it is available in an RV park, it is quite common for it to cost from $3 to$10 per day for service. Many truck stops do now have it available and you can get an annual subscription for service, but there are several providers so the cost can run up quickly. But it is great when you have it in an RV park.
The next choice is the "air card" that is available from both Cingular and Verison. With one of these you can get unlimited service for a monthly fee, usually about $60. They do provide a high speed connection and can be used anywhere if the signal is available. The coverage is improving, but is still far from everywhere so check the coverage maps.
The most available internet choice is the dish. While it is effected by weather, it can be use virtually anywhere and is a high speed connection. The most convenient dish system is an automatic one and those will cost about $5000 for equipment and about $100 per month. But they are easy to use, quick and reliable. Next choice is the manual, tripod mounted dish. Those are much less expensive ranging from about $800 to near $2000, depending upon the quality of equipment, the level of dealer support and the training the owner receives. There are two companies that provide dish internet and if you are interested, I suggest that you do a lot of research before you choose. There are some pretty important differences between the two companies in service as well as a very wide range of support from the dealers. Some sell real quality equipment and service, and there are also some real junk dealers out there. But most dish users consider their system to be the best choice, no matter which company they get service from, as long as they get good equipment.
It does take a seperate dish that is larger than the TV dish to get internet, but there are kits available to mount the TV equipment to the dish you use for internet from both service companies.