This one is so simple that I don't know why I even bother...
Anyway, here are a few views of the prototype:
It plugs into both supply rails and in the bottom view you can see that the output is pulled to whatever the inner rail is. For clarity I've marked the two pins of the tact switch, which when pressed connects the output to the outer rail. Therefore, depending on which side of a breadboard the buttons are placed, they either act as pull-down (left) or pull-up (right).
When I drew the schematic and board of the remake I was unsatisfied with the utilization of board space, which is why I added footprints for an optional low-pass filter. Though there's no footprint for SMD tact switches it should be possible to solder these to the through holes as well. I would have liked to also accommodate 3mm wide switches but I haven't figured it out yet.
So far there's only one button but this could easily be expanded (to fill a panel). I'm also thinking about a version with multiple buttons with proper debouncing using Schmitt triggers. Here I'd use a larger IC package instead of individual packages for every button but I'm not totally set on this.
This board has been superseded by this modified one but the ideas outlined here still apply for the modification. For updates please refer to the linked log.