But oddly not http://www.cryptopals.com/

Not so odd, I don't always use nor redirect www either (well I do if it's for a client, but otherwise I usually can't be bothered).

Edit: But I do get 404s when I click the "language-links" on the challenge pages, like http://cryptopals.com/sets/1/challenges/1/ruby. What are those anyways?

Well, it's strange to have a record for the www. subdomain and not do anything with it, like 403 :P

They are Solutions. The C++ one to the first exercise works:

http://cryptopals.com/sets/1/challenges/1/cpp/

It's probably the only one that works, and it's just a hint (the conversion function is weird btw, it accepts hexadecimal symbols ranging from '0' to 'z'; it actually "decodes" any base from binary to triacontahexadecimal (36)).