a coworker of mine wants to buy a new video card for his PC but is a tad overwhelmed by the array of choices (and price ranges.) He's into Call of Duty and games like that. Can you recommend a good card that won't break the bank (sounds like a game enthusiast as opposed to a diehard GAMER.)
What video card you can use is highly dependent upon your PC's motherboard. Recent PCs (something purchased within the last 12 - 18 months) probably have a PCI Express slot for graphics cards, older PCs (2 years or older) likely have an AGP slot for graphics cards. Don't confuse PCI Express slots with a plain old PCI slot. Check your PC's specs first, or crack the case open and check yourself, before spending actual money. If unsure, find someone who can tell the difference and get them to check.
Having said that, you're really just limited by the amount of money you want to spend and how much power you want to pay for per hour that you have your PC turned on. Modern graphics cards can suck a lot of power and run very hot, necessitating extra cooling, which means more power.
Once you get above $100 (the "budget" range), there's not really any bad choices between ATI-based cards and Nvidia-based cards. You're really just differentiating on price, features (like TV-out support) and performance. I normally don't spend more than $150 on a given graphics card, and for that much, you can typically find a decent enough card for occasional to frequent gaming (5-20 hours/week). You can certainly pay more than that, and depending on what your games need for good performance, you may want to shell out up to $300 if you spend a lot of time in front of your monitor (40+ hours/week). Paying more than $300 is really just silly, in most cases; if your games are still running slow with a $300 graphics card, you need to fix or upgrade other components in your system.
Right now, you'd want to get at least an ATI Radeon x1600-based card or an Nvidia GeForce 7600-based card for gaming, with a minimum of 256MB onboard memory. Higher product numbers typically indicate newer, faster hardware, and for Nvidia chipsets, you also have "trim line" codes (GS, GT) which indicate either lower-end (GS) or higher-end (GT) components on the card. If you want to spend the time geeking out and reading AnandTech or Tom's Hardware or HardOCP or other hardware review sites to see which chipsets and manufacturers give the optimum performance or best bang for the buck, you certainly can; but in general, if you spend more money, you'll get a faster and more capable card.
There are many many many different graphics card "manufacturers" (ASUS, Sapphire, XFX, Diamond, eVGA, MSI, Powercolor), but for the most part, they're producing reference implementations of either ATI or Nvidia chipset designs on their cards. Some folks look for cards that bundle free copies of games or software with the card, others look for faster memory or better cooling on the card, but honestly, there's not a huge amount of difference between them. I've had good luck in the last 5 years with Sapphire (midrange cards), Rosewill (low-end/budget cards) and eVGA (all price levels). Best thing to do with a given card is check user feedback to see if there's multiple complaints about a single issue (drivers, overheating, poor manufacture quality) and if not, it's probably fine. Real lemons do exist, so look for products that lots of other folks have tried out to make sure you don't end up with one.
Try checking on newegg.com for cards, they have a huge amount of user feedback on their items, plus competitive prices, excellent shipping and wonderful customer service.