QuantLib is a cross-platform, quantitative finance C++ library for modeling, pricing, trading, and risk management in real-life. It is also wrapped as Python/Ruby/Scheme modules. Extensions for Excel, R, and Mathematica are available. Other such extensions are under consideration. QuantLib offers tools that are useful both for practical implementation and for advanced modeling. It features market conventions, yield curve models, solvers, PDEs, Monte Carlo (low-discrepancy included), exotic options, VAR, and so on.
Ruby PHP Serializer is a Ruby module providing workalikes of PHP's serialize() and unserialize() functions, enabling it to manipulate serialized PHP data structures. It supports Array, Hash, String, Fixnum, Float, NilClass, TrueClass, FalseClass, and Struct, and has some support for arbitary object handling.
The Atom Publishing Protocol framework for Ruby aims to simplify the implementation of Atom Publishing Protocol (APP) support in Web applications. It achieves this by implementing a framework that handles the protocol-level duties for the programmer, while not making any requirements for the site design.
utf8proc is a library for processing UTF-8 encoded Unicode strings. Some features are Unicode normalization, stripping of default ignorable characters, case folding, and detection of grapheme cluster boundaries. The library can be used in C programs, but most of the functionality is also available as a ruby library. For PostgreSQL, there is an extension providing a function for preparing strings in case insensitive indices. The currently supported Unicode version is 5.0.0.
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.
FlexiRecord is a Ruby library for object-oriented access to databases (object-relational-mapping/ORM). Each table is represented by a class, and each row of that table is represented by an object of that class. This library is especially aimed to properly support database transactions. Currently, only PostgreSQL (version 8.2 or higher) is supported as a backend.