This is my personal list of online resellers who won't try to scam you, they charge reasonable prices, and offer good-quality merchandise.
For things like hard drives, mainboards, peripherals, and accessories, look no further than NewEgg. They've been in business for over twenty years (formerly Egghead Software). Prices are always competitive, although not necessarily the lowest. Shipping charges are never excessive and often free. Every product can be reviewed by users, so it's easy to find the high-quality stuff.
One should never pass up checking Amazon.com, just in case they have it for less than NewEgg.
This is a tricky market to navigate. There are literally hundreds of fly-by-night and bait-and-switch shops luring you with unbelievably low prices, only to gouge you later with exorbinant shipping, overpriced accessories, and dubious warranties. Check the website resellerratings.com before you buy electronics from any online seller.
Or save yourself the trouble and buy from one of these two retailers:
B&H Photo and Video. One of the few photographic stores in New York that is not a scam. Professionals shop here. They have a massive brick-and-mortar store in New York with knowledgeable staff. Prices always beat your local camera store, though be sure to factor in shipping to make sure it's worth it.
There's always trusty Amazon.com, too. They stock all the popular cameras and accessories, often at prices that beat even B&H. Some of their stuff is cross-listed with B&H competitor Adorama, whose prices and service are just a tiny notch lower than B&H. I have no qualms about ordering from Adorama.
Everyone needs cables, whether it's to hook up your new Blu-Ray player to an HDTV or simply have a spare USB cable laying around. Want to know a secret? You don't have to spend $50 on an HDMI cable or $20 on a USB cable from your local electronics chain store. You can get cables of equal or higher quality from Monoprice at a fraction of the price. Don't fall for the overpriced brand names such as Monster Cable; generic ones of high-quality construction will do just as well. Here's a sample of what Monoprice has to offer:
Premium 24AWG 6 ft. HDMI 1.3a cable: $9.98
USB 2.0 6 ft. cable: $0.94
10 ft. Category 5e network cable: $1.28
Business Cards, Flyers, Postcards
Want high-quality, four-color, press-printed business cards on thick cardstock instead of photocopied cards from your local office supply store? Check out America's Printer. Based in Los Angeles, America's Printer will accept your camera-ready documents (PDF, JPEG, InDesign, Illustrator) and run them on Heidelberg presses with a matte or glossy finisg. One thousand cards for under $40. Do keep in mind that you're expected to deliver files that exactly meet their specifications. They will not adjust your files or otherwise hold your hand in any way. You get what you ordered, whether or not it's what you wanted.
A couple of caveats: First, although they accept electronic upload of files, the job order has to be filled out by hand and faxed in. I don't know why. Second, it will take a couple of days from the time you submit your job to when it runs on the press. Even if you pay for overnight shipping, it will take at least 4-5 business days to receive your job. Finally, as with any third-party vendor, expect that your order will be messed up somehow and factor in extra time to re-run the job. They'll re-do it for free, but you'll lose about a week. On the other hand, you may end up with two sets for the price of one.
The inkjet printer manufacturers have spent millions to convince you that you need to print out your digital photos on one of their products. You know that the ink costs more than Dom Perignon champagne, right? Why pay that kind of money when you could get beautiful prints at a fraction of the price from your local Costco? There are dozens of online photo printing sites, such as Shutterfly and Photoshelter, but if you have a Costco nearby, there's no reason to go elsewhere. (OK, there's one; see below.) Costco will allow you to upload your files using a web browser and choose the print size. ICC color profiles of their Noritsu printers are available for fine control over exact color matching. About an hour later, pick them up at the one-hour photo desk. Prints are cheap: 17 cents for 4x6 and $2.00 for 8x10.
But when you want very high quality, such as printing a photo for exhibition, a wedding, or a gift, go to White House Custom Colour. They're a bit more expensive that Costco, but what you get is calibrated color prints on premium-quality Kodak Professional Crystal Archive paper. Prints can be as small as wallet-size and as large as 30x45, including huge panoramics. Your order will be carefully packaged in a plastic bag protected by layers and layers of cardboard and shipped to you via 2-day UPS for free. They can even bind your photos into books and matting/framing service is available. But as with any vendor geared toward professionals, they won't hold your hand. You're expected to know what ICC Color Profile is, how to use the sRGB color space, and how to crop to the exact dimensions and PPI they need.
Keep an eye on any of the Deal News sites, which include Deal News, Deal Mac, and Deal RAM. Every day they post a list of the best deals found around the Internet for gadgets, computer parts, clothing, TVs, flash cards, computer memory, and brick-and-mortar sales. All of the retailers featured have been vetted, so you won't get scammed.