BostonDrumBuilders.com
An excellent resource for information on some of the earliest New England drum makers. Its the #1 resource for information on George B. Stone & Son, Nokes & Nikolai, F.E. Dodge, and Stromberg drums. Owned by percussionist/collector Lee Vinson, it has frequent updates with new drums he's acquired and his restorations are simply beautiful.
DrumArchive.com
DrumArchive.com is a wonderful collection of free drum catalogs in pdf form.
NotSoModernDrummer.com
NotSoModernDrummer magazine was started by John Aldridge and George Lawrence. It frequently features articles by well-known drum collectors.
Olympicdrums.com
Olympic drums is a great resource for buying vintage drums. They also do great restoration.
VintageDrumsTalk.com
VintageDrumsTalk.com is great website devoted to vintage drums owned by Jim Messina. He is a major figure in the collecting world and host of many youtube videos recorded at the annual Chicago Drum Shows
VintageDrumGuide.com
VintageDrumGuide.com is a very useful resource for catalogs and information on the major makers, such as Leedy, Ludwig, Slingerland, etc. Their homepage also features early Ludwig catalogs, a Dodge catalog, and a rare 1910 Yerkes sound effects catalog.
CymbalExcellence.com is a site run by a friend and mentor of mine, Tom Stubbs. His instructional videos on cymbal playing are particularly fun and helpful.