My first attempt had mixed success. It consisted of a packet exchange between the PC and the robot using the now discontinued Parallax RF modules. However, the modules did present a number of problems and I decided to go a bit more expensive. I invested in the Linx setup (linxtechnologies.com). That ended up much better.
I plopped down the $300 for the demo boards (which included two transmitters and two receivers) and a few days later I got the above equipment in the mail. The demo boards are quite necessary for someone like me - I actually am glad I was forced to buy them. To start off, I set up a data exchange between the PC and the robot (one way) using just the demo boards. The receive demo board went on the 'bot and, after getting my protocols right, I put the robot on the floor in my basement electronics/computer room (read that - Fibber McGee's closet) and navigated it through the maze of junk that keeps collecting in the place - out the door, down the hall, back to the room and to my chair. Three curious Golden Retrievers followed it back into the room. I just hooked the PC up to the transmitter board, hooked the receiver board onto the top of the 'bot and ran the output to a Basic Stamp. The Stamp interpreted the PC commands (using the SERIN command) and relayed the commands to the motor controller (see previous html page). Fairly straight forwards.
OBTW: I am not an expert at RF (far from it) - so I'll say again - the Demo boards helped a lot. The instructions from Linx are very good and have many valuable hints. I used them all! Also, if I hadn't had the demo boards, I would have probably screwed this up - the demo boards convinced me that the modules worked and worked well. It was really convenient a couple of times (right after I thought I might have smoked the Rx/Tx modules) to plug in the demo boards and verify that all the RF stuff worked.
See where the 16F84 is? That's because it screws up the transmitter (and receiver) when it is too close. Also, I couldn't get a 10 MHZ version to work at all. I had to drop to 4 MHZ to get it all to work in this small of a package. The 10 MHZ version of the 16F84 was just generating too many harmonics. It took a while to figure all this out (groan!).