Here’s some links to interesting Ruby information. I intend to update it periodically.

Ruby Doc – Best site for looking up the core Ruby API and the standard libraries.

AllGems – Documentation for most Ruby gems.

Ruby Forum – Mirrors of the main Ruby mailing lists. Some are read-only.

Gemcutter – The new gem hosting site.

RubyForge – The old Ruby project hosting site. It is slowly being phased out.

Try Ruby – The new Try Ruby page, where you can go through an interactive tutorial directly in your browser.

Ruby Inside – Popular Ruby blog, with frequent articles.

Ruby Flow – Community-submitted Ruby links.

Ruby Trends – View and vote for trends in Ruby software, books, and more.

Ruby Pulse – Screencasts of Ruby software and libraries.

Ruby Subreddit – Reddit site for Ruby. Not incredibly active.

Ruby Stack Overflow – Ruby questions on Stack Overlow.

Confreaks – Not strictly Ruby, but videos from many Ruby events are available for streaming.