Digilent Basys 2 using TinyOS-nesC
Do you understand that the Basys2 card is an FPGA-based card, not a microcontroller? You have to use an HDL (such as Verilog or VHDL) to program the FPGA.

If you program the FPGA to contain (possibly among other things) a microprocessor, then you might be able to use the TinyOS/nesC programming environment on that processor. You would have the choice of either porting nesC to, say, the Microblaze CPU that Xilinx provides (such a port may already exist, but it's hard to tell with a casual search), or implementing a CPU in the FPGA that already has nesC ported to it.