eBay: You can find almost anything on eBay, especially hardware items and motors. There seem always to be foot throttles; plenty of steering wheels; gearshifts; bow eyes and handles; control cables; propellers; seats; deck plates; instruments; trailers; aluminum for jack plates and steering arms.... Outboard motors sell briskly on eBay, as well as parts. Start searching for stuff as soon as, or before, you begin building your boat. And keep going back. Some of the suppliers listed on this page, like West Marine and Harbor Freight, also have eBay stores.
Epoxy and related supplies
U.S. Composites: Very good prices; this is where I've been buying my epoxy
System Three: I've used this brand with good results
Galeton: Gloves and other protective gear
Midwest Marine Plywood: 4340 Main St, Saint Bonifacius, MN 55375. (952) 446-9611
Noah's: I have purchased from these folks and was very satisfied.
Chesapeake Light Craft: Kit boat maker, also sells okoume marine plywood. Excellent shipping rates on small orders. "I would highly recommend using them.... The packaging was perfect" according to one of my GT Pro builder/racers.
Plywood & Door
Sorensen: Hydroplane and runabout plans and kits, and racing hardware including steering gear.
Brown Tool and Machine Co., Inc.: "All the hardware you need for Outboard Motor Racing"
Machined Components: Racing Products
Portage Bay Systems: "a tradition of quality since 1934"
Wintech Engine and Machine: "... acquired the assets and exclusive rights to ProFast/Nydahl steering equipment and racing controls."
Lifeline: Racing life jackets and other safety gear
Security Race Products: Life jackets, etc.
Deist: Race and motorsports safety equipment, including life jackets
Defender: Discount boat and marine supplies
West Marine: Huge selection of boating supplies for all types of boating
Surplus Center: I get steering shaft bearing here, and water pressure gauges.
Harbor Freight: Lot's of discounted tools and supplies and even boat trailers -- shipped KD via UPS. Also a good source for tarps. Coupons available.
Galeton: source for disposable gloves and coveralls.