Having gone well over 100K miles on bicycle, I've found CST 1218 to be the most durable tire by far. They are inexpensive and resist punctures very well, too.
Caveats: they are a street tire, don't have the greatest cornering capability due to their profile and compound, and ride a little rougher than some others.
I currently have a set of red ones on my bike and haven't got a flat since I put them on 2 years ago. I've had other sets go for 20+K miles on pedal bikes.
link (for black ones):
http://www.amazon.com/CST-City-C1218-Tire-2-125/dp/B001645BPS/
Continental Town & Country are another amazing tire. Unfortunately, it's getting hard to find German-made ones. The non-German T&C are not as good.
Bicycles used by police departments in California typically use them and the tires often out-live the bicycles!
As mentioned by butre above, Maxxis Hookworms and Holy Rollers are very durable. It must be noted that CST and Maxxis are the same company.
It's getting hard to find Hookworms in 24 or 26" (they are out of production now), but Holy Rollers are still produced AFAIK.
Kenda Flame/Sun Flame look like a gimmicky flametread but this is deceiving. I have a set of these that are 7 years old with over 5K motored miles on them!