Josh French just wrote in that there is a new Ruby on Rails Akismet project on Ruby Forge. He says, “It’s a tiny bit smarter about grabbing some request info from the environment and more flexible when taking arguments to the public functions. Installs into the plugins dir rather than lib/, for maximum Railsyness.”
Anything with maximum Railsyness is A+ in my book.
Akismet 
We need a Rails version of WP! 😉
I agree with Jonathan!! Theres got to be a good solution that is like WordPress with “Railsyness”
also, that term, “Railsyness” is awesom.
Mephisto (http://mephistoblog.com/) is written in Rails but it doesn’t look like it’s quite there yet. I have chosen WordPress as my blog although I use Rails for development.
No one has mentioned Typo yet? (typosphere.org)
I’ve tried both Typo and Mephisto as a rails blog CMS, and Typo seems to be a bit more ‘there’ than Mephisto, although that might just be a matter of taste. Typo is very transparent in terms of configuration and management. It’s not /quite/ as feature-rich as WP, but the straightforward rails framework makes it easy to customize. For what it’s worth, I use it on my site.