Memory cards seem like the photographic equivalent to a package of tube socks when it comes to gift giving, but the fact of the matter is that they're necessary and having to buy them stinks. We strongly recommend shopping around reputable online retailers for the best deals on memory, as it is generally pretty easy to find manufactures offering rebates. However, do not purchase a memory card through auction sites like Ebay, as phony cards are quite common. The big brands like Sandisk and Lexar are usually very reputable and you might be able to score some serious deals on these if you're willing to brave the crowds on Black Friday.
You'll need to find out whether you're in the market for Secure Digital (SD) or Compact Flash (CF) cards, but that information is easily obtainable if you find out the model of the photographer in your life's camera. Most photographers are more than happy to talk about their cameras if prompted. Trust us. Keep in mind, CF cards are generally slightly more expensive than SD cards. While you can easily procure a 16GB SD card for $20, chances are it will run you about the same price for any 8GB CF.