Multi-model forms with attribute_fu
I've used attribute_fu in two of my projects now. In one of them I use it in three different places. It simplifies your code a lot, when you want to edit many models in one form. Strongly recommended!
Gradual switch to resource_controller
resource_controller is a plugin that allows your controller's code to ... disappear :-)
A great thing with this plugin is that you can introduce it gradually. Just install it, and make one controller a resource controller. See how it goes, and then decide whether it was worth it. I did it like that, and now I'm switching to it wherever I can.
BTW, both attribute_fu and resource_controller are made by James Golick. Thanks, James!
restful_authentication with RSpec
I didn't know it before, but Bartosz Blimke discovered that, when you have a spec directory in your Rails app and you generate some resources using restful_authentication, then it will generate Rspec specs instead of unit tests. Cool! I'm not a big fan of code generation/scaffolding, but when they also provide good specs then it easies the pain.