I make 'em as I need 'em. (Until then it's just junk that makes my life harder and 90% chance it eventually ends up in the trash can rather than needed.) Toner or credit card. Made one, today, for a uC.
Having just made one, here are a couple of things I did:
ICSP header, obviously.
Integral decoupling cap pad, check.
Add some extra prototyping area in empty space.
Add a SOLDER pad for every pin, because you never know.
For the micro, I added one LED+resistor on the breakout not attached to anything. Just two extra pins/pads. Can jump or wirewrap to w/e pin I care.
Similarly added pads for an SMD PFET, sourced to VDD, with pullup pad, gate resistor pad, and a series pad on the drain for increasing the output impedance if necessary. Drain and gate attached to floating pads/pins.
Might want to add an LED for power verification. I shoulda done that.
Use long breadboarding pins that go into the breadboard AND extend out the top for wire wrap.