I'm not a ruby/rails guru, but I've just started a blog using Mephisto at http://www.flyingmachinestudios.com/blog . My first two articles are on thinking about mental models in regard to user experience - not strictly rails, but I plan on writing an article on creating a macro for Mephisto.
There's also Rick Olson's blog, http://weblog.techno-weenie.net/
