A few years ago, I wrote https://github.com/0x20/backtab to sell drinks at the local hackerspace; it's worked well so far, and the backend has a fairly simple REST interface.

Since then, my flatmate got me interested in the AS/400 hobbyist community, and before long I had found myself the proud owner of an IBM Power 750 Express server running IBM i, with no idea what to do with it. I've wanted to use COBOL for a real project for a while, and porting the backend seemed like a fine excuse :-D

It's been slow going because the IBM docs are extremely dense, but the project so far has convinced me that if IBM i were available to hobbyists at a reasonable price, it would be a much bigger player in the market. Building simple CRUD-style apps is trivial, with the "GUI" design being almost VB-levels of easy.