ObjectSpaces First Look
The project I've been working on for over a year now uses an object-relational mapping layer to persist its business entity data to SQL Server 2000. Because of this, I've been involved with a team who has evaluated almost every third-party tool/library that's currently available. This is a space that is beginning to mature, but there is still a very wide disparity in the products that are available. Microsoft has been talking about its ObjectSpaces technology for a few years now, and MSDN just published a First Look article that's worth reading.