General hardware

• McMaster Carr — The BEST place to find anything mechanical or hardware related. Even about a bazillion types of screws. Tools, plumbing, hardware, even stock materials like metal and sheet rubber. They're the "Amazon" of hardware.
• Grainger — General items, tools, supplies, etc.
• Small Parts „ Screws, tubing, and other materials available in small quantities.
• OnlineMetals — Small order raw/stock metal source. Also starting to carry some plastic too.
• Ridout Plastics — Anything plastic related.
• Craftics — Another good plastics source.
• Specialty Bottle — Bottles, jars, vials, and tins of all sorts.
• House of Antique Hardware — For antique hardware and reproductions, as well as decorative electrical switches and outlets.

Electronics

• DigiKey — One of the best sources of electrical components.
• NewArk — Another electrical component source.
• Jameco — Electical components, and especially tools.
• Oznium — LEDs

Computers and modding

• Cables-To-Go — Any type of computer or A/V cable.
• PC Connection — Computer parts, cables, and networking products.
• FrozenCPU — Computer parts for case mods.
• CrazyPC — Another supplier of computer parts for case mods.
• Xoxide — Computer parts for case mods.

Photography

• B&H Photo Video — All things photography related.
• Cord Camera — (local) One of the best photography supply shops in southern Ohio.

Paper crafts

• John Neal Books — Book binding tools and supplies, caligraphy and instructional materials.
• The Paper Studio — Decorative and specialty paper.
• Paper Wishes — Scrapbooking supplies and decorative/speciality paper.
• Ranger Ink — All kinds of specialty inks, dyes, stamp pads, etc.

Other stuff

• The Gemmary — Antique scientific instruments.