Pretty much any K6-2 / Pentium MMX will run in a Socket 7 board. The Cyrix MII and MediaGX+ CPU's can also run in a Socket 7 board. The K63 can as well, but it is very picky about what chipset it lives with.
The trick is to get a board with a SiS, ALi, or VIA Chipset. I recommend VIA over all the others. Some companies also ignored Intel and bolted a 440HX (instead of the more common VX and TX chipsets) chipset to Socket 7 boards. Didn't really do much except allow the later 266MHz and 300MHz PentiumMMX (NOT Pentium II, that mobile CPU is an entirely different beast, and NEVER ran with the Socket 7 crowd).
Super 7 was a socket 7 board with AGP and USB. A lot of them had breakout cables for Serial, Parallel, and USB. I remember working at a mom 'n' pop shop for a few years during the Socket 7 / Socket 370 / Slot 1 / Slot 2/ and Socket 478 heyday. Building a Super 7 machine was easy, but trying to stuff all those extra cables into a mATX Tower case was not fun.
Super Socket 7 brought some of these technologies to the dying, but still cheap Socket 7 platform:
The 100MHz system bus (75Mhz for Cryix and some AMD at 85MHz and 95MHz)
AGP 1x, 2x, 2x w/sidebanding, 4x
Onboard USB / Firewire
ATA66
On board NIC (most high end Socket 7 boards had this, but it was the $50 super socket 7 board that made it more ubiquitous.)
Basically Super Socket 7 was to bring all of the new cool stuff from the Pentium II machines to the Socket 7 architecture. It did a pretty damned good job of it too. So much so that Intel released the 266MHz Pentium MMX and 300MHz Pentium MMX (both formerly only mobile CPU's) for Socket 7 because AMD was beating them in that arena. At this time in history the Slot A Athlon was still on the drawing board.