ChucK official site - http://chuck.cs.princeton.edu/ (or http://chuck.stanford.edu/)
Downloading ChucK - http://chuck.cs.princeton.edu/release/
ChucK Language Specification (1 hour read) - http://chuck.cs.princeton.edu/doc/language/
Examples - http://chuck.cs.princeton.edu/doc/examples/
ChucK UGen Library - http://chuck.cs.princeton.edu/doc/program/ugen.html
"Secret Menu" of ChucK features not in the rest of the documentation - http://chuck.cs.princeton.edu/release/VERSIONS