If you are looking into building a teardrop, I highly recommend lurking around a teardrop forum and checking out many of the beautiful trailers that others have built. Even if you decide to purchase a ready made trailer from one of the many vendors, these forums are filled with ideas and techniques to help make your trailer your own. I have found the members of these forums to be extremely helpful and more than willing to help a new 'teardropper' out.

I also recommend watching the forums for dates and locations of teardrop gatherings that may be going on in your area. Most teardrop owners seem to be used to people asking them questions about their tears and there is no better way to get ideas and resolve problems than checking out another teardrop up close and in person.

This is a list of sites that I have been using for help, inspiration and planning.

Forums:
Teardrops & Tiny Travel Trailers *
Teardrop Talk

Plans:
Generic Benroy (free) *
Teardrops and Other Trailer Designs (free)
Trailer For Two (free)
The Weekender (free)

Big Woody Camping
Camping Classics *
Desert Teardrops
Kuffel Creek Press *
Li'l Bear Tagalongs
The Squidget
Tin Top Teardrop

* My primary references.

Parts:
Big Woody Camping
Camp-Inn Teardrop Trailers
Li'l Bear Tagalongs
SoCal Teardrops
TeardropTrailers.net
Vintek Vintage Trailer Supplies

Builders/Dealers:
American Teardrop Trailers
Big Woody Camping
Bubba's Trailer Park - Retro Style Camping Trailers
Camping Classics
Camp-Inn Teardrop Trailers
Cozy Cruiser
Desert Teardrops
Lassen View Custom Teardrops
Little Guy Teardrops Camper/Trailer
Locke Nest Trailer Replicas
Mini-Tears
Silver Tears
SoCal Teardrops
Tears O'Joy
Toter Teardrop
Vacations in a Can
Wee-Kender
2 Phun Teardrops

Helpful Data:
Galley Gallery
Lumber Dimensions
Rubber Roofing Installation Guide
This to That (Glue Advice)
Tongue Strength
Trailer Balance
Trailer Balance (theory)
Weight Estimates (PDF) (Excel)
Woodworking Tips