Looking for some great sources for your electronic parts? This list gives you some perennial favorites, both inside and outside North America. This list is by no means exhaustive; you can find literally thousands of specialty outlets for new and used electronics.
Plus, Amazon and eBay provide virtual marketplaces for all sorts of sellers — from established retailers to individuals selling parts and components out of their homes. But the sources listed here are among the more established in the field, and all have web pages for online ordering. (Some also offer print catalogs.)
North America
Check out these online resources if you're shopping in the United States or Canada. Most of these outlets ship worldwide, so if you live in a different country, you can still consider buying from these stores. Just remember that shipping costs may be higher, and you may have to pay an import duty, depending on your country's regulations.
All Electronics
All Electronics runs a retail store in the Los Angeles area and sends orders worldwide. Most of its stock is new surplus, meaning the merchandise is brand-new but has been overstocked by the company. All Electronics has a printed catalog, which is also available in PDF format on its website. Stock changes frequently, and the latest updates are available only on the website.
Allied Electronics
Allied Electronics is what's known as a stocking distributor. It offers goods from a variety of manufacturers, and most parts are available for immediate shipping from Allied's warehouse in Fort Worth, Texas. Allied is geared toward the electronics professional, but it welcomes hobbyists, too. The Allied catalog is huge, and it's available on the website as well as in print. You can also find parts using the search feature on Allied's website.
Digi-Key
If you want it, Digi-Key probably has it. Like Allied Electronics, Digi-Key is a stocking distributor, carrying thousands upon thousands of items. Digi-Key welcomes small orders and offers reasonable USPS shipping rates. Its online ordering system includes detailed product information, price, available stock levels, and even links to product datasheets. The site offers a handy search engine so you can quickly locate what you're looking for, as well as an online interactive catalog (with magnification capabilities you'll need). Digi-Key will also send a free printed catalog, but to read the tiny print, you have to get out your glasses. The text has to be teeny-weeny to fit everything in.
Electronic Goldmine
Electronic Goldmine sells new and surplus parts, from the lowly resistor to exotic lasers. Its website is organized by category, which makes ordering easy. (One category, labeled "Rare and Esoteric," may be where Doc Brown got the flux capacitor that made time travel possible in Back to the Future.) Listings for most parts include a color picture and a short description. Be sure to check out the nice selection of project kits.
Jameco Electronics
Jameco sells components, kits, tools, and more, offering both convenient online and catalog ordering. You can browse the website by category, or if you know the part number you're interested in — such as a 2N2222 transistor — you can find it by entering the part number in a search box. You can also use the search feature for categories of parts, such as motors, batteries, or capacitors. Just type the category term, press Enter, and off you go.
Mouser Electronics
Similar to Allied and Digi-Key, Mouser is a stocking distributor with tens of thousands of parts on hand. If you can't find it at Mouser, it probably doesn't exist. Mouser carries more than 165,000 resistors alone, listed in the "Passive Components" category. You can order from its online store or its humongous print catalog. Feel free to request a printed catalog to keep on your nightstand, or let your mouse do the walking through Mouser's online catalog.
Parts Express
Parts Express specializes in electronic parts and other equipment for audiovisual aficionados. You'll find an ample selection of individual components, complete with user reviews, as well as project kits and other do-it-yourself resources on the Parts Express website. Check out the project showcase, comprehensive list of formulas (including Ohm's Law), and technical glossary, and don't forget to review the electronics safety information. You'll also find Parts Express on eBay, Facebook, and Twitter!
RadioShack
RadioShack is perhaps the world's most recognized source for hobby electronics, but alas, "The Shack" filed for Chapter 11 bankruptcy in early 2015 and the future of its brand is uncertain. As of mid-2015, roughly half of RadioShack's 4,000 retail stores were in the process of closing, but it's likely you can still find a location within reasonable driving distance of your home. If you need a resistor, capacitor, or transistor right away, you definitely won't find it at Wal-Mart or BestBuy, but you may find it at your local RadioShack. RadioShack also has an online store, RadioShack.com, but you might receive an "out of stock online" message when searching for components. Fingers crossed that the local stores survive and thrive!
Outside North America
Electronics is popular all over the globe! Here are some websites you can visit if you live in places such as Australia or the UK. As with North American online retailers, most of these folks also ship worldwide. Check their ordering pages for details.
Premier Farnell (UK)
Based in the UK, but with operations in 24 countries across Europe, Asia Pacific, and the Americas, Premier Farnell stocks some 500,000 products. It operates under several company names, including Farnell element14 (Europe), element14 (Asia Pacific), Newark element14 (North America), and Farnell Newark (Brazil). To order products, start on the web page, select your country from the extensive list on the home page, and you'll have access to a vast array of products.
Maplin (UK)
Maplin provides convenient online ordering for shoppers in the UK and the Republic of Ireland. The company also supports dozens of retail stores throughout the UK and Ireland.