Berkeley DB XML is an open source, embedded XML database created by Sleepycat Software. It’s built on top of Berkeley DB, a “key-value” database which provides record storage and transaction management. Unlike relational databases, which store data in rel

free oss – comes with .net libs and single dll embedded version
Firebird is a relational database offering many ANSI SQL standard features that runs on Linux, Windows, and a variety of Unix platforms. Firebird offers excellent concurrency, high performan

Lucene.Net is a source code, class-per-class, API-per-API and algorithmatic port of the Java Lucene search engine to the C# and .NET platform utilizing Microsoft .NET Framework.
Joel Spolsky says this is what the excellent lookout was built on top of.

php implementation of 9-block IP address visual display.IP address -> glyph.
perhaps I can make a wordpress plugin for it