Whenever I get I get tired of dealing with all of the disconnected layers of Rails, I think about how I should really write a decent component architecture that works well on top of it. Luckily, someone has already done it for me.
From the Cells homepage:
Cells brings the benefits of component-oriented development to the Ruby on Rails web application platform, without the performance problems that had been associated with Rails' own, deprecated, component subsystem.
Each Cell is like a little lightweight controller (with associated views) that you can embed anywhere in your app. I've been playing with it tonight, and while it's not on the level of say, Seaside, it seems like a fairly good baseline for building a more component oriented system for your apps.
I know from a mailing list that I'm on that some people are kicking around taking this and building a stateful component framework with real object binding underneath. That would really take Ruby web frameworks to the next level. (And be a ton of work to get right, I'm sure. :-) )
Hopefully that project will get started soon. I'm extremely interested in watching and helping it develop.