What are your favorite lesser-known gems/plugins for Rails?
This question about Rails plugins brought up only the usual suspects (Paperclip, RSpec, Shoulda, Restful Auth, etc). It'd be great to get a list going about the hidden, less popular ones that rock.
I've been using cache_money a lot in projects recently. Its given us a huge performance increase
I just started using App_Version. It's nice to be able to put the version of the app that your running on the bottom of your page (Like the "svn revision" number on the bottom right-hand corner of this page).
Dr. Nic's Magic Models Not that i actually use this gem on any of my projects, I just thought it was cool when it was first released. Dr. Nic also did a hack so if you made typos in your code it would guess what you meant, so very very wrong.. but funny as hell.
I'm really liking delayed_job for asynchronous tasks it's simple and effective. Been using it for async mail with great success.
responds_to _parent lets you do ajax-like things with file upload forms (which can't use real ajax.) But you can also use it anytime you want to send RJS to the parent window.
Also, a bit of self-promotion. I really like my plugin soundex_find, which allows you to handle misspellings and phonetic matches in auto-completers or searches.
Another one i've found I'm using more and more is andand, this gives you guarded method invocation.
Instead of
entry.at('description') && entry.at('description').inner_text
you write
entry.at('description').andand.inner_text
It's been saving my fingers lots of typing in the last couple of projects.