I'll second what someone else said about the Altera boards, there's a
lot of bang for your buck in them.

If cost is a concern, you can ditch the boards all together and do the
whole thing in simulation. Put Altera's free Quartus II web edition
software on a PC and teach from that. The waveform simulation is quite
good for instruction purposes.

For varying levels of abstraction, Quartus (and the Xilinx equivalent)
allows you to 'code' in purely graphical terms, by drawing a schematic
of gates, etc. This is very good for introducing basic logic. Then
they can move up to VHDL or Verilog.

I'm not sure about college level, but a good introductory university
level text is Brown and Vranesic. It does things in VHDL.

One thing I would stress is to make sure that your students understand
how synthesis from VHDL is done and good VHDL coding practices (i.e.
writing hardware rather than trying to write software). I TA a course
where the lab component is done in VHDL and I find the students do
much better if explicitly instructed on how VHDL synthesizes, rather
than just learning VHDL syntax and winging it. This may seem obvious
but our problem is finding time in the curriculum to do this on top of
dealing with the real course content (processor architecture).