This isn't an instructable to actually make a female USB connector, but to get them out of a PS/2 to USB connector (those delivered with about every USB mouse and keyboard)

Some steps might be obvious but I try to include as much tips as possible to make it easier.

Step 1: What You Need

You only need a PS/2 to USB connector (the little blocks delivered with every keyboard, mouse and computer).
If you don't have one lying around, try asking any of your friends (especially if they recently bought a new computer, keyboard or mouse). Usually companies or schools will have them lying around so try there also.

You will also need an exacto knife (or similar sharp knife). I find the blade pictured the easiest to use. I also used a sturdier blade later.

Step 2: Cutting the Converter Block

Cut the block along the visible seams on the sides.
Don't rush this, if you press too hard all you'll do is break your blade.

Barely press on it the first few cuts, so you have a guide for the next cuts.
After a few cuts, you can press a bit harder but make sure your blade isn't bending. If it is, there's a high chance that it will break or try to turn.

It might not be obvious when you're through, as there's plastic on the inside also. Try to pry the edge apart if you're not sure if you cut deep enough.

When you're all through on both sides, the outer plastic will come apart pretty easily. It might be glued in place, but it didn't require too much force to get it off for me.

Step 3: Separating the Female USB Connector

You will see the PS/2 and USB connector now, connected by some plastic with wires running through it.
You can cut it in half (about the middle should work) and proceed, or just go on without cutting it in half first. The plastic is quite soft and I didn't seem to have trouble getting through the wires either.

With a bit of luck, you can pull the plastic right off the female USB port (the case for the purple block). You just need to cut off any wires that stay on.

If it doesn't come right off, cut along the edge of the USB connector all the way to the pins. I recommend the sturdier exacto blade here.
Then, by pushing your blade in from the side, cut over the top and bottom of the pins (the plastic on that one being semi clear helped a lot).
Do the same thing on the sides of the pins (just all the way left and right, no need to cut inbetween the pins) and the ends of the pins.

Now, most of the plastic should come right off, leaving a bit of it between the pins. You can just pry that out of there.

Now you're left with a female USB connector to use as you wish.