[plt-scheme] gentle intro to the new FFI?

I can see, in 299, foreign.ss -- and it's mighty intriguing.  I've
already gotten it working, a little, but haven't figured out all the
details.  The combination of documentation and examples probably
contain all the information that I need, in theory, but it's pretty
terse, and I haven't been able to figure it out ...  Is there anything
else written that demonstrates the proper use of foreign.ss?
-- 
Okay, a word about VoteHere: This is the company that has no
visible means of support.  It doesn't seem to sell anything.
        -- Bev Harris, blackboxvoting.org