They work pretty much like any cartridge-bearing bottom bracket, but instead of having a fixed cup with a flange that bears on the bottom bracket shell, and a mobile cup with a lockring, each cup effectively acts as the lockring for the other. Both bear directly against the central cartridge unit, or against a central sleeve that also protects the innards. Sometimes, each cup has its own lockring.
Models I know of are Phil Wood, WTB, Race Face, TA, Mavic, Miche, a few older Campag (Athena and C-Record)...
I'll bet there are plenty more.
Bacause many bottom brackets are designed around standard bearing dimensions (often 28mm or 30mm) you can often get away with using the flangeless cups from one manufacturer to mount another manufacturer's cartridge: Miche cups fit some Stronglight cartridges, for example, while WTB and Phil cups fit Shimano (UN70/71/72) cartridges.
You generally get a few mm of adjustment side to side, but that can be limited by the depth of thread in the frame.