I don't want to start a flame war here but you might want to check
out the changes I made to OpenBSD's s/key stuff a few years back.
I support md4, md5, sha1, and rmd160 and adding additional hashes
is as simple as writing 2 stub functions.  Code for sha1 and rmd160
with the same interface as the md4/md5 routines can be found in
OpenBSD's libc/hash dir.  Additionally, I implement rfc1938 with
the exception of custom dictionaries.  If you have any questions,
feel free to contact me...

 - todd