index.rb is a general indexing framework for Ruby. With it, you can create collections of documents, then index and search them. The traditional inverted index is supported, as is Latent Semantic Indexing (LSI). Input documents may be stemmed, to make user queries more general. It also provides TextTiling to break input documents covering multiple topics into topic-specific sub-documents.
Lich is a cross-platform multithreaded interpreter meant exclusively for use with text-based MUDs. Its primary goal is to provide a dynamic and extensible framework that offers advanced users the ability to customize the application and its functionality to their needs while remaining accessible and useful to the majority of players. It supports scripting in Ruby, Simutronics "Wizard", and, in Unix environments, any language with an interpreter program.
Injection is a simple dependency injection plugin for Rails. It allows you to inject ojects into your controllers which have been described in a yaml file (config/objects.yml). By using constructor injection for controllers, it becomes easy to test the controllers use of such objects using dynamic mocks.
The Ruby on Rails SubList Plugin makes it easy to have dynamic lists of related models on a single editing page. The plugin is designed for models with one or more has_many relationship with other models. By using AJAX for adding and removing "sub-forms", one can present the user with a single edit page that creates/edits the parent model as well as all of the children.
Tartan is a text parsing engine targeted at wiki text. The syntax specification is defined in YAML in the form of regex-based rules. It supports layering and multiple output types. Rules for Markdown to HTML are included, with optional layered extensions for tables. It is implemented in Ruby, but looking to have implementations in other languages.