Hi, Connie, your inlaws sound a lot like mine! I always try to go practical with them. They have so much "stuff" sitting around the house already. Last Christmas I gave them some stationery that I personalized with my computer/printer, envelopes w/ their return address/ address labels/ postage stamps and note cards. Another year I made a calendar with old family pictures printed on each page. I suspect someday when they're gone and the kids have to go through their house, we'll find all the gifts we ever gave them stashed away in closets.
We also have to buy for teenagers we don't know very well. If they're driving, I usually get gas gift certificates. If not, certificates for movies, video rentals, fast food places... I usually attach the certificates to a small gift, like an ornament or a key ring or some candy.
I never thought of subscriptions - I'll have to put that on my ideas list for this year (along with the "swift kick in the pants" idea).