Object Oriented Database
Having been involved in developing many RDBMS based applications over the years, I was quite interested in researching into Object Oriented Databases and happened to stumble upon Perst.
I must say I was quite impressed, and hopefully the future of databases will follow this kind of example in the future. Another bonus is the fact the source code is also provided.
Lets hope that the new Sql Server(Yukon) has some object oriented features to aid in future .NET database applications.