Md-rails gives you an instant Markdown template handler thats compatible with Rails 3. It also comes with some generators so you can automatically build with Markdown, not that you'd ever want to. But still, :boom:!

Twitter Bootstrap Form helpers

Add media types supported deserialization using your favourite parser

Add media types supported serialization using your favourite serializer

MemCacheFragmentStore correctly handles errors and reuses the CACHE object rather than creating new clients.

helper and controller macros to define current menu item and also create the menu in view.

This gem will revolutionize the menus.

Safely merge params for use with url_for or for the query string

MergingQueue is a simple gem for grouping tasks by type and time using the ActiveRecord ODM framework and background jobs

Metaa adds meta tags to your Rails application with ease.

Want to get a path to an AR object, but don't know what the object is? Want to set a controller's instance variable, but don't know what controller you're in. Meta Magic can help.

Write highly focused and testable view presenter classes for your Rails controllers and actions

A gem to create meta tags easy!

metasploit-framework

Simple metatags and page titles for Rails.

SubdomainRoutes add subdomain conditions to the Rails routing system. Routes may be restricted to one or many specified subdomains. An URL will be recognised only if the host subdomain matches the subdomain specified in the route. Route generation is also enhanced, so that the subdomain of a generated URL (or path) will be changed if the requested route has a different subdomain to that of the current request. Model-based subdomain routes can also be defined.

Michael HintBuble allows you to generate hint bubbles and tooltips in Rails applications using the same syntax used for rendering templates.

Helper for microformats, possibility of nesting.

Action processing with Callback + Rescue handlers for different MIME types in Rails

MiniAuth is a pragmatic authentication gem for Rails that is inspired by Laravel's guards pattern that provides highly customizable and simple authentication for your web applications and APIs.