Mango seems interesting, thanks for that. I got thrown into a tight spot at work, where I'm building a lease calculator for the accountants, I need to build the whole thing as a self-contained application, due on Monday. Long story is that it wasn't as easy as I thought, and I ended up having to replicate Journal entries, a trial balance and financial statements. Even though Mongo doesn't have transactions, I found a good way to make my journals balance. I'm using aggregating framework to post journals to TB and FS.

The last part I was worried about is the self-contained bit, so I'm going to give CouchDB a try, and use Mango to prevent redoing everything

You don't need a different NoSQL database, you need a relational database.

I would assume a SQL database would be at least a tad easier to do accounting like tasks?