I would like to build my own .100 (2.54mm) cables to mate with standard single and double row headers, but the 'rectangular connectors' section of distributors websites is huge. Which ones do you recommend? Can you recommend an IDC system that works with discrete wires (not ribbon cables)?
well, almost all of them that aren't specifically designed for ribbon cable or other specific cable types will work fine with discrete wires.
Most of the easy to use ones aren't true IDC connectors as jeanne mentioned, and generally speaking the crimping tools are really expensive for small scale work ($150 for the tool, which is really just a pair of pliers in the right shape is normal). You can hack crimp them and solder carefully and be fine.
TBH any of the rectangular connectors in the correct shape/spacing are fine. Look for the ones that best match your wire and look easy to crimp without the proper tool.
As far as i can tell in the production world its more or less a battle of who can provide the best automated tools for assembly as it is which shroud/crimp is 'better'.
The twisted wire bundle things works OK as long as the signals on the wire don't have integrity issues. If they do, do not try it.
I ran into very much the same problem in the past when having to connect 2 pcb's together with relatively high frequency signals (multiple channels of ~3mhz I2S). We ended up using the very thin plastic style ribbon cable (FFC or Flat Flexible Cable), the stuff you see on LCD screens or inside cell phones.
I don't honestly to this day know a good supplier for small quantities of this stuff. I just asked our factory in china when they normally used and they sent over a bunch of connectors and cables for me to test and match the impedance of ( i think it was 3M's FFC series but not sure).
Worked great but I had a hell of a time attempting to find that stuff myself without it costing a fortune, like $5 for a 3inch cable, but like $0.40 from the factory. If you can find it cost effectively, it really makes life easier for good controlled impedance interconnects.
If you do find FFC parts for a reasonable price in low quantity let me know how :)
We've used ITW PANCON "MAS-CON" series connectors. (single row, available in 0.1" or 0.156" spacing) They work pretty nicely, the crimper tool isn't very expensive.
It's not exactly what you asked for, but check out EMSL's article on Twisted Wire Bundles.
We have the correct crimping tool, which is something like this (but that may not come with the right die for those specific pins).
It's expensive, but then it's actually a bit more complicated than a regular pair of pliers. For one thing, it ratchets. When you put the pin in it and start to ratchet it closed, the die will line up and hold the pin while you insert the wire, so you don't feel like you need three hands. And unlike ordinary large automotive/appliance type crimp connectors, it doesn't just crush a tube in which you've inserted the wire. Rather, the die bends the tabs of the connector around and into the stripped wire, and bends the other tabs around the insulation. And it has an adjustable stop, so it will crimp each pin the same regardless of how hard you squeeze it.
But that's for production work. For hobbyist use, you could roughly crimp these with small pliers, then carefully solder them.
Why do you want to mate to [EDIT] standard, straight, unpolarized, non-locking [/EDIT] .1" headers? I'd strongly suggest going with something that's locking and polarized. The AMP-Latch and mini-JST series both fit the bill [EDIT] and have a 0.1" pitch. [/EDIT] Mini-JST needs a crimper, AMP-Latch has both crimping options and IDC (designed for ribbon cable, it will work with discrete wires but I don't think you'll find anything marketed as such). Remember that you can use .098" connectors as well, don't limit yourself to 0.1" for the 2/1000ths of an inch.