I've used some excellent suppliers, so I figured I'd gather that info in one place for others to benefit from.
My favorite suppliers:
Aircraft Spruce: General supplier of aircraft grade parts and components.
SteinAir: I've gotten misc. less common parts like the shunt, relays, pitot/static tubing, etc.
McMaster-Carr: High temp grommets, threaded rod, etc.
Belmetric: Good source of metric hardware (and it's 20 minutes from my house, so I've actually gone there if I really needed something quick).
BoltDepot: Another source of metric hardware.
AircraftSpecialty: Got my brake hose custom made with them. Contact Steve.
SkyGeek: Great source for airplane stuff at excellent prices.
ProwireUSA: Great prices on aircraft-grade wiring (better than Aircraft Spruce).
ANHoseFittings: For AN hose fittings! I ordered high-temp Adel electrical/hose clamps from here.
Digikey: Good for misc. electronic parts.
Amazon: Misc. tools and some parts and materials (as long as I can confirm it's of known provenance and quality).
Onlinecomponents: I bought AMP branded ring terminals from them for my 6AWG charging circuit wiring.
MSC Industrial Direct: Good source for Oetiker clamps.
Pegasus Auto Racing Supplies: Good source for fuel filters, clamps, fittings, and even AN bolts (I haven't done it, but it would be worth comparing the pricing to Aircraft Spruce), etc.
Gamut: Good source for barbed fittings.
GripLockTies: Mike Patey says these are best, so that's good enough for me!
