I used to use both 26 and 24awg wires stripped out of Mogami cable scraps that I had from making cables. The crosslinked polyethylene doesn't shrink back as quickly as pvc or normal polyethylene (although not as good as teflon), it came in different colors to keep track of channels, and it was relatively inexpensive. They were pretty flexible with a bit of spring to them, which made keeping them in an exact position tough sometimes. You can get the 26awg out of the Mogami 2893 mini quad cables, giving you 4 different colors at roughly $0.80 a foot for the group. The 26awg is more finely stranded than the 24awg so keep that in mind if flexibility is a concern. 24awg comes in clear or blue out of the Mogami 2534 quad cable at $1.12 a foot. You could alternatively use install cables which have identical internal structures and are usually cheaper. They are also harder to find not in spools. Mogami 2799 ($0.64) is the mini quad, and Mogami 2820 is for the regular size.
I have also used some silver plated copper in different sizes from John's Teflon Shop on ebay. These wires are pretty slick and sometimes stripping the wires can be just a tad tough. They aren't as finely stranded as the Mogami so they ended up being stiffer, which I actually liked because it helped keep wires where I wanted. Prices vary, but roughly $0.30 a foot if you aren't picky about color.
I have also used DHC Nucleotide UPOCC copper in clear polyethylene. This is my favorite wire for making headphone cables and interconnects, but the shrink back of regular polyethylene requires very precise soldering. Once I get better with soldering inside enclosures and in closed in areas, I might switch back to this (especially since he has black in addition to clear now), but I still prefer something with teflon for now.
I am currently using some 26awg finely stranded silver plated copper in teflon. These wires have a slightly thinner teflon cover and with the fine stranding, make them very flexible. They have a slight bit of memory which is helpful, but nothing like the SPC from John's Teflon Shop. I got them from a HiFi shop in Taiwan, but they no longer have it listed for sale. I got it at about $1 a foot, and it is very nice. Supposedly 5N purity. On occasion, John's Teflon Shop has thinner, more finely stranded wire that is very similar in usability for a little cheaper, but not in a pretty clear teflon (I know you most likely won't see it).
I have no idea if there are sound differences, as I never built the same thing twice to compare.
Edited by FraGGleR - 10/2/12 at 7:20am