I definitely suggest checking out spork.
http://spork.rubyforge.org/
The railstutorial specifically addresses this, and gives a workaround to get spork running nicely in rails 3.0 (as of this moment, spork is not rails 3 ready out of the box). Of course, if you’re not on rails 3.0, then you should be good to go.
The part of the tutorial showing how to get spork running in rails 3.0
http://railstutorial.org/chapters/static-pages#sec:spork
Checking when spork is rails 3.0 ready
http://www.railsplugins.org/plugins/440-spork