Worth it: Larger size, good resolution relative to size, image quality
Skip these to save: DisplayPort, exceptional refresh rate
Buy from third parties: Cables
PC displays have only subtly improved recently; you're not likely to notice any difference between a new product and one designed a couple years ago. So shop well to save money.
Look to hardware reviews to gauge differences between old and new models. Be cautious if a display is touting exceptional stats; it's likely to be priced higher to reflect those specs.
Be sure the reviews support the manufacturer's claims, too. Most specs aren't standardized, and they vary among manufacturers.
You need only a display with a DVI port that supports HDCP (High-bandwidth Digital Content Protection). HDCP is necessary for playing copy-protected files, namely Blu-ray movies and some HD downloads. Nearly any DVI display from the past few years should qualify.
Additional ports--such as analog inputs, HDMI, and DisplayPort--can be handy if you want to connect devices with those options, but they'll usually add more cost. Avoid nearly obsolete displays with VGA-only capability.
Pick a display size that's comfortable for your desk, with big enough resolution. No hard rule exists, but I like a screen to have a resolution higher than 1920 by 1080 pixels (1080p) when it's larger than 22 inches.
Worth it: Low-cost-per-page printing
Skip these to save: Extremely high speeds, wireless networking
Buy from third parties: Cables, ink (if quantity is more important than quality)
Example: The Brother HL-5370DWT laser printer is a few years old and slower than new models, but you may find it now for as low as $250, down from $300 last spring. This laser printer outputs a still-satisfying 26 pages per minute, so it's a good buy for small offices and networked homes.
Manufacturers often list the rough number of pages through which an ink cartridge will last; use this information to calculate and compare the price-per-page cost of each printer you consider.
New printers continue to promise faster and faster page output, but most people won't notice a difference between 24 pages per minute and 18 ppm. If you're not churning out big files regularly or printing in great quantities, even slower rates can be enough.
Additionally, built-in wireless networking on a printer can really boost its cost. If you want a network printer, buy one with ethernet capability, and attach it to your wireless router. Your wireless PCs can still connect. You can share a regular USB printer on a network whose computers use most popular OSs. For more, read how to share the printer when one PC uses Windows 7.