UPDATE: I have made an improved and simplified pin connector library that I would recommend instead of this now: http://www.thingiverse.com/thing:213310. This V3 library may still be best for certain situations, but for most, I think you'll like the new one better.
This is an update for tbuser's awesome pin library. I've been making enough use of these that I found a few changes that I think improve them significantly, though this should still function as a drop-in replacement for the V2 library. For all the people who've had trouble cramming the pins into my heart gears, this may help you make easier pins.
The primary changes are:
1) Wider gap keeps the pin nubs from getting jammed in a tight hole
2) Tolerance parameter on the pin side (instead of the hole side) because it's easier to reprint new pins if the fit is wrong
3) Extra tolerance parameter on holes (only for loose fit)
4) A fixed hole option that completely prevents rotation
5) Pinshaft module for making solid pin sections for longer pinpegs
6) Different pin sizes now have a more consistent shape
7) Minor changes to hole shape
Put pins.scad in your working directory and call it with the "use" command in your OpenSCAD file. Read through pins.scad for directions on using the modules (it's mostly very similar to tbuser's original).
UPDATE: At the request of PrettySmallThings, I've made this library customizable. That won't affect its usage in OpenSCAD, but now you can export custom pins and holes using Customizer, to import into your other CAD programs. I still suggest learning OpenSCAD, but now you can avoid it a little longer.