I'm running 26 inch wheels on my gravel grinder. The list of tires is obviously smaller for 26 inch wheels than 29ers. Some of the Kenda tires come in 26 inch flavors but they're not easy to find online.
I like pasela t serv protite tires which comes in a 26 x 1.5 and a 1.75 (although it measures a little narrower than spec).