How long have the accounts been open and what is their credit limit relative to your total credit limit?
If these are accounts that have been open for many years and their combined credit line represents a large portion of your total available revolving credit, I'd leave them open unless you are very confident you won't mind the hit on your credit score for a couple years. If these are recently opened accounts and represent a small percentage of available credit, the hit to the credit score (if any) may be small enough that it's fine to just simplify things and cancel them. If you don't plan to use these again, I'd actually cancel them actively rather than letting the accounts age.
For example -- I have a Visa from my CU which I almost never use since there's no cash back or other rewards attached to it. However, I've had this account open since the early 1990s and has a $20,000 credit limit, so losing this account could put a decent hit on my credit score. I charge $10-20 on it about once every 3-6 months to keep it open. I don't know that my CU is known to cancel accounts to inactivity, but why chance it?
Having said that, I'd recommend making sure you always have two cards. Sometimes weird things happen and your primary card may be refused for some reason (system glitch, your card number flagged as compromised by the bank, et cetera) -- in which case it's good to have a backup.
"Hey, for every ten dollars, that's another hour that I have to be in the work place. That's an hour of my life. And my life is a very finite thing. I have only 'x' number of hours left before I'm dead. So how do I want to use these hours of my life? Do I want to use them just spending it on more crap and more stuff, or do I want to start getting a handle on it and using my life more intelligently?" -- Joe Dominguez (1938 - 1997)