scheme48, because scsh, the scheme shell uses the VM of it. and, of course, Guile - because i am GNU/Debian user and it provides as far as i can see the best interface to C and implements a great part of the POSIX stuff from scsh (sockets, threads et c.). it provides also quite a good console-environment with debugger and the ability to backtrace (same as with MITscheme and Drscheme, i guess). for emacs i use the cmuscheme-package , which has great syntax highlighting and never let me down yet...i got also some of the Sunterlib packages, but was too stupid to get them installed properly. there a also a lot of stuff for generating html and parse xml on Oleg Kieselov's page i have downloaded and want to test in the nearer future. would be a great thing, if someone experienced writes an scheme-module for the nginx server. the server itself is poorly documented, but there is a tutorial in english for the module environment.