Rail Mail is a Rails plugin by Scott Fleckenstein that stores copies of any mail that your Rails application sends, and provides an interface to view it.

Aidan Finn has written what may be the most comprehensive walkthrough of developing an authentication system in Rails. He starts from the migrations and covers every step of the process, right through to the tests. If you want to see how a Rails developer produces an entire block of functionality from start to finish, this is worth reading.

Rodney Ramdas has put together a small application called "Learn Ruby" that shows the freely available version of the Pickaxe Ruby book alongside an instance of irb, meaning you can work through the examples and tutorials more freely. Note that it's for OS X only.

RailsTidy is a plugin for Rails, by Damien Merenne, which validates your RHTML templates, the HTML output from your functional tests, and tidies up the HTML generated by Rails.

Settings is a new plugin for Rails that lets you have a basic hash of 'settings' or configurations for your application without having everything hardcoded. Example:

It's a few months old, but this guide to creating your own role based authentication system in Rails is pretty good. It doesn't use any plugins other than the LoginGenerator.

RailsHelp.com has possibly the simplest homepage in the world. Just type in what you're searching for, and off you go. It's a nice change to digging through the regular API documents.

If you're on Windows and have been having trouble with your database adapters, this post about new Ruby database adapters for Windows might just be for you. Now, back to TextMate... :)

A few months ago I was getting fed up of having to create new ActionMailers from scratch on my Rails applications, so I decided to come up with a 'generic' way to cover all the bases. Instead of creating multiple mailers, you create a single mailer and append generic methods. The content goes to the regular RHTML files and you send through whatever you want from your controllers. See Simplifying ActionMailer development in Ruby on Rails. There's probably a lot that could be done to it now, but it works great for me.

Michael Gorsuch demonstrates how to add SSL to your Rails app in 5 minutes. Very simple and very effective.

Craig Webster has posted several times over the few days about his adventures with sockets in Ruby. He provides nice code examples (even doing socket stuff direct from irb!) and his explanations are useful if you know what you're doing with Ruby, but haven't tried doing any TCP or socket work yet:

When using Rails it's easy to forget there's any other way. Sometimes, however, it's useful to access databases outside of that environment. Luckily, ActiveRecord can be used separately from Rails, and Craig Webster demonstrates how.