Either the LOGi-Pi or the LOGi-Bone, with the LOGi-EDU package.
The EDU package is built to allow you to follow the examples in either one of these books:
http://www.amazon.com/FPGA-Prototyping-Verilog-Examples-Spartan-3/dp/0470185325/
http://www.amazon.com/FPGA-Prototyping-VHDL-Examples-Spartan-3/dp/0470185317/
There's also a bunch of demos on their wiki.