I like the Continental Travel Contacts and their 26X1.75 rides like a narrower tire on hardpack. Pressure can be dropped off road. Very versatile, smooth and easy rolling, durable, and flat resistant.
The Panaracer TServ is a nice tire for a 26" mtn bike commuter as well. Available in 1.25, 1.5, and 1.75. The 1.75 - 2.0 width on a 26 tire is the sweet spot for me.