That's a really general question :-P If your goal is robot vision, then I'd go with C, and I'd use OpenCV, which does most of the computer vision stuff for you (I'd also be using a PC, rather than a microcontroller, since a uC might be too underpowered for the job).
Most of the robots I've worked in have been programmed in C or Assembly. Assembly is *fast*, and most microcontroller programming programs take C code and convert it into assembly. Problem is that most uCs have their own versions of assembly language, and I've always found that the programmer is just much better at optimizing my assembly code than I am, so I tend to stick with C.
That being said, many industrial robots are moving towards languages that are easier to use, like C# or Java. Some hobby robotics uCs use visual basic (the Basic Stamp being the most prominent example of this).
My recommendation is to learn C and learn it really, really well, though. I've encountered C far more often than anything else, and PICs can be programmed in C, along with many other microcontrollers.
As for the actual packages to use, it depends entirely upon your project. If you're using the Axon microcontroller, then the libraries for its uC and the utilities built by Admin are a must. If you're using a PIC, you may even have to write some of the libraries yourself. As I said before, computer vision and OpenCV are a good match, although probably not the only one out there.
What kind of project are you working on?