For our son: At Michaels, they sell little things for cheap and I got one of those wooden train whistles (sounds good!), hot wheels or a motorcycle, a recorder or harmonica (we don't mind the noise as long as it's NOT electronic), a cap, a comic book, and of course the orange, apple, mixed nuts, and candy canes that I grew up with. I have a little plastic box where I collect miscellanious stuff I come across throughout the year (usually starting in August when I'm more cognizant of the upcoming holidays)---he loves Spiderman and I found a little square Spiderman washcloth that expands and grows when you put it in water, or dinosaur eggs that grow, or a cool soccerball twisty straw, whatever. Little things that are interesting but not something I'm just gonna buy on a regular basis...this year I also found a neat travel cup that's personalized with his name on it.
For my husband: Again, we do the orange, apple, candy canes, mixed nuts. I add a little thing of his favorite candy which I have to go to the British Emporium to get, so it's a rare treat. Once (many years ago) when we were dating we discussed Christmas traditions and laughed that we had the same food staples in our stockings even though we were on different continents...and I said "and of course you got the hot wheels cars" but he was poor and said "in your STOCKING? that was a main present for us"....so now, every single year he gets a hot wheel in his stocking. I try to make it commemorative of something we've done that year (an event where we got to take our son on a firetruck got him a firetruck that year, or a long flight on vacation got him an airplane, before kids we rented a jaguar on vacation and that scored him a jaguar in his stocking, that kind of thing). I try to find a special ornament for each of us (one a year) and those, too, go in our stockings and we can laugh/talk about it and then hang it on the tree til New Year's Day when we take the tree down. His favorite ornament was an old English phone box b/c he's a Dr Who nerd. He likes games so sometimes I'll get him a pack of Uno, or the Scrabble cards where you make words on top of words instead of just the board game, etc. I slip in little love notes and/or an elaminated comic strip that was SO him, stuff like that. A small updated picture of the family for the frame on his desk at work. Perhaps a gift certificate for a great date: I've done that for an after-Christmas dinner at the Reata that he really liked (had a babysitter arranged and all that; all he had to do was get dressed). If your husband collects something, this is a good place to put an addition to his collection. Itunes cards, I do like. I usually get the little liqueur chocolate set, or some Godiva truffles because I love them so! Have fun...the stocking is the most fun to me because there's no "pressure" to finding a specific thing, and we like it to be personal-something that proves we know who they are/where they're at right now, or to commemorate another great year together.