This past summer I was looking into DIY coil leashes to make some bright you-can't-miss-me-orange dummy cords for my kayaking gear, and came across
this method on EDCForums. Unfortunately at the time, I had none of the recommended monofilament line, and the already-coiled keychains I tried to pull paracord over were just a millimeter or so too large for the outer sheath. So, I went paddling anyway. But tonight, thinking about how I'm going to braid a towel hanging line for the bathroom in my new apartment (rather than cough up the money for a metal bar and wood screws), I realized the line I have now, might actually do the job.
Editor's note:
knightoftheroad, your sock review post is coming, I promise! 
The idea was to take this:
And turn it into this:
How do we do this voodoo magic? We heat the monofilament line into the shape we want (using boiling water) and then cool it quickly to set it.
1) Cut the paracord and monofilament line to desired length.
2) Gut the paracord and push the monofilament inside of it instead.
(You will see recommendations to melt the monofilament to the end of the p-cord's guts, and then just pull the inner strands on the other end to gut the pcord and insert the monofilament in one smooth motion. This is a REALLY GOOD idea that I skipped, because my 24" line was spunky but not belligerent.)
3) Coil your pcord/monofilament tightly around a wooden dowel and tape it in place.
(I used a wooden spoon. Because it's the first thing that came to mind. Also, electrical tape, because I'm low on other types of tape--wrap your coil tightly and your tape tighter.)
4) Don your protective gear. Bring some water to a boil. Once ready, dip the coil-wrapped dowel into the hot water and hold it there for a while. Internet recommended ten minutes. I discovered my patience level peaked at four minutes (hmm...yeah, I'll work on that).
5) Pull the dowel out and IMMEDIATELY a) run the coils in under cold water or b) dip the whole thing into another pot of cold water. As you can see, I did both. The basic idea is to heat up the monofilament enough to make it pliable, and then cool it into a new shape (your coil). After the sink, I left my dowel in the cool water for another five minutes.
6) Take the dowel out--it and the cord wrap should be cool to the touch--and unwrap the tape from around your coil.
7) The moment of truth: pull the cord off the dowel and check out its shape. A spiral? Success!
8) If you want your spiral to be tighter, take one end of the coil, thread it through the very center of the coil and pull it out to reverse the coil, giving you this:
I didn't need it to be that tight (maybe if it loosens down the road I'll do this), so I reversed it again, back to normal and then added it to the first awesome thing I could think of--my titanium spork.
!@#*#$%^& SUPER
BONUS LEVEL *!@#@^%^**
Do you pwn Super Mario levels like a BOSS? Tossing Koopas into each other like bowling balls to knock Yoshi free just in the split second you need him to slurp up a key and leap into the secret keyhold that your 15-years-of-gaming-experience friend sitting next you HAD NO IDEA EXISTED?
Yeah? Then you should try this water-less version of the DIY paracord coil:
* Find some paracord. Preferably
blue.
* Find some phone cord with less diameter than the pcord. Maybe also
blue.
* Melt the phone to the inners of the pcord.
* With a flourish
and your best finishing move face, gut the pcord and string the phone at the same AWESOME MOMENT.
* Melt the ends of the pcord sheath and the inner phone cord together. Crimp the ends with appropriate keychain hardware.
* Add split rings, carabiners, and attach to your blue phone cord-wrapped katana.
* Post a picture.
*
Profit.
