I was reading another post in the forum and thought that it would be a good idea to start a thread where we share the different sources for DIY gear. I have seen similar posts on forums at backpackinglight.com.
Here is my contribution...

Quest Outfitters (www.questoutfitters.com)
Outdoor Wilderness Fabrics (www.owfinc.com)
Denver Fabrics (www.denverfabrics.com)
Strapworks (www.strapworks.com)
On Rope (www.onRope1.com)
Speer Hammocks (www.speerhammocks.com)