While I'm not yet sold on the idea of cell phones as gifts (really, a two-year contract is the gift that keeps on taking), I have to like AT&T's new mobile phone holiday gift finder.
It's a Flash-based Web site that lets you easily pick out the cell phones your loved ones will want based on their tastes, though I think it would be more handy for people who are looking at signing themselves up with AT&T or those looking to upgrade.
Whatever the reason you're at the site, you'll like the sliders on the left that allow you to select from basic to cutting edge, personal to business, form to function, and communication to entertainment. You can also mouse over each individual phone to see its features at a glance.
You can even sort by the type of plan your giftee has (contract or prepaid), and browse accessories. If they're happy with their gear, you can always get a ringtone gift card. I hear they look good in stockings.