STG Soundlabs make 5U modular amongst other things, they are also behind the Knobcon event itself. We spoke to Moot Booxle about the the muSonics modules - starting with a VCA based on the Moog 902, and also the MooSonics - which is a budget more DIY range with PCB panels available as DIY kits first, then prebuilt later.
More info http://stgsoundlabs.com
If you want a compact sampling workstation
Standalone twin osc, twin filter machine
Moog Rothenberg and more
We take a look