The Dextop application framework allows you to create Rich Internet Applications based on .NET/Mono and Sencha Ext JS. It has proven to be useful for online business applications. It features a desktop-like Ext JS frontend, simplified client-server communication, a stateful programming model, real-time updates and notifications from the server, automatic column model generation, automatic store model generation, and automatic form generation.
Nearforums is a lightweight powerful discussion forum that can be installed within minutes on Linux or Windows servers with MySQL or MS SQL database servers. It includes great features like sign-in with Facebook/Twitter, navigation with tags, full Web administration, built-in search engine, RSS feeds, and accessible HTML. It is SEO friendly.
DeveelDB is an embedded SQL database management system for .NET, implementing all the features of the SQL92 specifications (transactions, triggers, procedures, functions, etc.). The aim is to provide .NET and Mono developers with a fully functional, powerful, and embeddable database system that can be used in several contexts, managing small to large amounts of data.
Voca is a vocabulary trainer for foreign languages. It allows you to create and manage your own word lists and share them online. You can make word lists for any language or for other things you want to memorize. It lets you do different types of exercises, including grammar, pronunciation, and picture tests. It lets you take tests with open answers, self-check, or multiple choice. Voca has support for multiple translations of a single word.