The other day I mentioned in freenode's #web that it'd be hilarious to see a web framework in scheme.. And now it has happened and it's not only making me giggle, but making me thoroughly impressed. Nice one!
The portable lib SLIB (a Scheme library that works across many Scheme implementation) also provides a lot of useful things for web development (html generation, database management, etc.).
The core of Racket, its syntax and basic constructs, is basically the small and elegant Scheme we all known and love. What set Racket apart is all of the additional features that was built around that tiny core (its own OO system, for example), as well as a huge standard library.