The mountain bike I've restored has spent all its time riding roads. I'd love a road bike but funds aren't up to it yet, so I was thinking about putting a pair of road bike tyres on and swapping with the mountain bike tyres when needed. I'm running 26x1.95 at the moment, and I'm wondering if I would benefit from a different size for the road. I'm assuming the 1.95 refers to the width of the tyre.
I think what you are looking for are a pair of "slicks" for your mountain bike. They come in a number of sizes for 26" wheels. Batman suggests looking for a set between 1.7 - 1.9" That is a good suggestion since you will be able to use the same tubes are are in your 1.95 mtb tires.
If you are willing to get a new set of tubes with those tires, I would suggest looking for 26 x 1.25 - 1.5" slicks. It is a matter of preference, but I find them to be a bit quicker and responsive if you are willing to run the associated higher pressure. If you commute has lots of curb jumping, pot holes, or broke pavement 1.75s may be my choice...
My experience is that 1.95 slicks really dont offer much over a fast rolling knobby tire.