Warmoth is a high-quality custom guitar parts manufacturer based out of Washington.  They have become quite popular among boutique luthiers.  I really like their stuff. 

Here is some information from the Warmoth website

We've been crafting fine necks and bodies for over 25 years. We are the only major manufacturer of these components in the U.S.A.! The others are primarily importers. Because we build our own parts right here, we can offer you far more options and custom details. So if you have some unique ideas and requirements, our online catalog is for you.

At Warmoth, "Quality is Paramount". Our entire operation is geared toward crafting excellence. That's why we're number one. Others talk it; we deliver it. We have supplied necks to Yamaha (900 Series Pacifica), necks and bodies to Valley Arts (Custom Pro Series), Pensa-Suhr, Sadowsky Guitars and many other quality-conscious builders. Be assured, we won't send you anything less.

Only select woods and proven construction methods are used here. Whether you are repairing a guitar or custom building one, you want parts that look good AND sound good. You get that from Warmoth. A lot of good hands work on these guitars. Guys that know what perfect is, ...and isn't. Everyone here takes pride in finishing their task in making your guitar part.

There are cheaper parts available, but hey, they come from the same factories that make cheap guitars. Don't be fooled! Our parts are guaranteed; if you don't feel they live up to our claims, send them back and we'll refund your money (see terms of guarantee and warranty).

Here is a link to the Warmoth Homepage.