I apologize for not posting any code yet, but I thought now might be a good time to shamelessly plug a project that I've started contributing to:
Object Persistence Framework 3 (on CodePlex)
Opf3 is an object relational mapping framework created by Christian Liensberger, Program Manager at Microsoft. It was originally a commercial project, but recently went open source on CodePlex. Opf3 was an extremely important part of my old job, which involved integrating a web application with a database system called Pervasive SQL. Opf3 was the only ORM framework with PSQL support out-of-the-box (at the time, at least).
In addition to Pervasive SQL, Opf3 also supports MSSQL, MSSQL Compact, Oracle (Microsoft's provider, but ODP.NET is being considered), Advantage Database System, Firebird, OLE DB, SQLite, PostgreSQL, MySQL, and VistaDB.
Keep checking back, because I hope to post some entries about using Opf3 in the future!