I am always looking for geocaching gifts for DH for Christmas, birthday, whatever. There are some nice things in the Groundspeak store, like geocaching.com t-shirts and geocache containers and stuff. They even have the "fake rock" geocaches. I got one of these one year for DH.
Geocoins are also always a fun gift. (Except my DH never wants to "release" his, he likes to save them, which to me takes the fun out of them, but if it makes him happy, that's all that matters.)
This year I discovered the geocaching stuff at Cafe Press - there are some really great designs for t-shirts or mugs or whatever. You can check them out here.
There are also some good gift items there in my sidebar to the right, sold by Amazon, that I recommend. Listed is a beginner's GPS that we think is good, as well as our GPS, which was somewhat pricey but has the features we felt we wanted after having been at this sport for awhile, and it has great accuracy, I might add. Also in that list is a first aid kit, which is a MUST, a Geocaching for Dummies book, and a backpack. The first aid kit and Geocaching for Dummies are good gifts for the beginning geocacher.
Finally, there's always a premium membership to geocaching.com if your loved one is not already a member. Geocaching.com offers a Premium Membership gift certificate which can be used to upgrade a basic membership to premium, or if your loved one is already a member, they can use it to extend their current premium membership another year (scroll all the way to the bottom of the page to see that option). Great gift for the geocacher who has everything!
If you have any other good ideas for geocaching Christmas gifts, tell me! :-)