We are planning on holding a "Refinery CMS Day" on the 30th of July. The purpose of this day is to fix as many issues related to Refinery CMS as possible so that we can support Rails 3.1 when it is released. Head over to GitHub issue list to see currently reported issues and let us know if you're able to help on any of them.
Translation revisions are also more than welcome. Currently Refinery CMS is translated into 22 languages so it would be really cool if all of those translations would be complete and up to date. There are also guides which could always be supplemented in order to help new users.
To sum it up - if you're willing to improve Refinery CMS in any way and you're free on the 30th of July, please join the #refinerycms (irc.freenode.net) IRC channel and see what people are working on. Almost all of us (core developers) will be there at some point (timezone differences...) and we'll do our best to answer all of your questions.