Most off-the-shelf desktop systems come with pretty weak video cards. That's fine if all you're doing is checking e-mail and browsing the Web, but if you plan to get into gaming, photo editing, video production, and other graphics-intensive areas, you'll need a lot more video horsepower.
Thankfully, upgrades are fast, easy, effective, and affordable. For example, Newegg has the EVGA GeForce 9800 GT 512MB video card for $49.99 shipped. That's after a $35 mail-in rebate (PDF).
This isn't the fastest card on the planet by any stretch, but trust me--it's plenty fast. I have the same one in my HP tower, and I can play most games at maximum resolution with all the effects cranked up.
The GeForce 9800 GT features 512MB of DDR3 RAM, a PCI Express x16 interface, and three outputs: VGA, DVI, and HDMI. EVGA backs it with a two-year warranty.
The requirements are a bit steep, however, so make sure your system can accommodate this card. It needs a 400-watt-or-better power supply, two physical slots' worth of space, and an available 6-pin power connector.
Because it's HDCP-compliant, you can connect it to an HDTV and enjoy Blu-ray movies (assuming your system has a Blu-ray drive) and other protected content. Toss in one of the upcoming CableCard adapters and you'll have yourself a killer home-theater PC.
I remember when cards with this much horsepower would set you back $200 to 300. Amazing what you can now get for 50 bucks.
Bonus deal: Speaking of home theaters, BuyDig has the Panasonic SC-BT230 home-theater-in-a-box for $275 shipped. Specs include a Blu-ray player with support for Netflix, Pandora, and Wi-Fi (with an optional adapter); 1,000 watts' worth of 5.1-channel surround sound; and an iPod/iPhone dock.