I just received the Microsoft Kinect for Developers from Amazon. I intend to use it as the primary sensor for my robot; It has a lot of interesting features including an IR sensor, depth sensors, audio, camera, and a fantastic set of API's. For the cost -200.00 U.S. dollars- it seems like the easiest place to start. After the unboxing I downloaded the Kinect SDK and Developers Toolkit
and spent a couple days playing with the code. The two main development languages are C# and C++ and are numerous examples using both - I chose C# to get started.
A side note, I have never coded in C# before, but I was able to get up to speed with the help of some tutorials posted by Microsoft
I spent a couple hours and was able to figure the rest out from there.