As the answer above suggested, there is an effort on writing a "spec" on http://ruby-std.netlab.jp.
You have to be careful with that "spec". It is not done by the language designers, and they are basically documenting what they see and not the other way around. It is based on 1.8.7 therefore there may be features in 1.9 that are not covered.
I can't imagine myself remembering the syntax with a 300 page document. To have "over the table", this cheatsheet describes what you want: condensed syntax, reserved words, etc. This is an alternative from dzone.
