After using relational databases as back-end storage all my Windows programming life (currently .NET), I want to experiment with a document-oriented database by this Wikipedia definition; it can be standalone or layered over an existing non-commercial database system.
What open source document-oriented database solution would you recommend from your own Windows programming experience and why? (Reason for open-source is to keep it on the cheap, also because open source is often darn good and on the leading edge.)
A nice to have would be a .NET provider to connect with.
Ultimately the chosen system might be rolled into a real solution if everything works out well.
Admittedly this is somewhat subjective and potentially argumentative so keep it real folks and I'll do the same - also your answers will be invaluable to others looking into document-oriented databases for the first time on Windows. I'm sure the overall value of your answers will outweigh any biases.
Thanks.