I've been doing the switching supply thing a lot lately, it seems.
I think the next thing I do might be something along the lines of a bench power supply.
I don't need something hyper-isolated or lab quality, but I would like something that would have a constant voltage output combined with an ammeter.
My thought is that if I start with a very standard 18 VDC, 5A unregulated supply (that is, nothing more than a transformer, bridge rectifier and a big filter cap), I can follow that up with an adjustable buck converter followed by an ammeter and a voltmeter.
I think that requires further consideration...