Community Engine is a free, open-source social network plugin for Ruby on Rails applications. Drop it into your new or existing application, and you’ll instantly have all the features of a basic community site.

Features of this social network plugin:

• Authentication (sign up, log in)
• User profiles
• User search
• Blogs with tagging, categories and rich text editing
• Photo uploading and tagging
• “Clippings” – visual bookmarks
• Commenting and comment notification by e-mail (Blogs, profiles, photos, and clippings can be commented)
• Forums
• Friendships and activity feeds
• Favoriting of clippings and blog posts
• And more!

Snipplr is a website where you can store / share your code snippets and find the ones that are already shared by other users.

It is great to find real-world working code examples with an organized interface which saves a lot of time.

Snipplr covers almost every language from ASP, ASP.NET, PHP to Ruby, Django or AS3.

A feature I like is seeing the codes shared by a specific user (nice feature for following users whose coding style is much familiar to you).

Snipplr is absolutely a must-bookmark for a developer.

It is a time consuming process to create an admin interface with standard functions such as add-edit-delete-update again and again.

ActiveScaffold, a Ruby On Rails plugin handles all the ActiveRecords smartly. It adds add-edit-delete-update functionality with an Ajaxed interface & sorting, searching and pagination support.

ActiveScaffold features:

• AJAXified table interface for creating, updating, and deleting objects
• Automatic handling of ActiveRecord associations
• Sorting, Search and Pagination
• Graceful JavaScript degradation
• RESTful API support (XML/YAML/JSON)
• Sexy CSS styling and theming support
• More extension points than you can shake a stick at
• Guaranteed to work on Firefox 1+, IE 6+ and Safari 2+
• Released under the MIT License, the same one as Rails itself, so you can use it freely in your commercial applications.

Datetime Toolbocks is a JavaScript library with advanced date parsing that generates date data from the text passed. A simple example would be "today", "next friday", or "last monday".

This smart date parsing JavaScript library also has a DHTML based date selector which makes the library vey functional for users who would prefer text or visual input selection.

DateTime Toolbocks currently supports Ruby on Rails as the development platform.

Radiant is an open source content management system built with Ruby on Rails. It is built for small developer teams other than the end-users as it requires programming knowledge.

With a very simple interface, Radiant offers flexibility when creating the design & content. 3 parts: pages, snippets (like PHP includes) and layouts create the core of the system.

It offers a flexible site structure where pages can be arranged according to any hierarcy.

Radiant has a custom template language named Radius (similar to HTML) which can be used inside pages, layouts to include content from other pages or display content conditionally & more. It also has an intelligent caching mechanism which helps serving pages faster while ensuring the content is up-to-date.

Redmine is a flexible project management web application. Written using Ruby on Rails framework, it is cross-platform and cross-database.

With a plain interface which makes the use easier, Redmine has most of the features a project managemnt software must have like multiple projects, role based access control, wiki & file management.

Redmine features:

• Multiple projects support
• Flexible role based access control.
• Flexible issue tracking system
• Gantt chart and calendar
• News, documents & files management
• Feeds & email notifications.
• Per project wiki
• Per project forums
• Simple time tracking functionality
• Custom fields for issues, projects and users
• SCM integration (SVN, CVS, Mercurial, Bazaar and Darcs)
• Multiple LDAP authentication support
• User self-registration support
• Multilanguage support
• Multiple databases support

Redmine is in beta status yet and improved regulary.