I have a '01 Toyota Tundra . What kind of mpg should i get? I think i'm getting around 14. 5 mpg. It has a little over 100000 miles on it.

Or where could i find out what i should be getting?

That is actually a lil low you should be getting about 18 - 20 mpg if its a v8. If u havenent had it done before I would reccomed going to a Toyota dealership and have a fuel induction service done on your truck, it should help out with your gas mileage.

Dadar,
I have a 2000 model V8 that I bought new, and have been getting 17-18 mpg (highway) since day one. I can't vouch for the induction (injection?) service recommendation, but I did pick up one little tip, fuel related.
If you get any rough running or stalling problems (which I did around 90k miles), remove the rubber boot that goes between the air cleaner box and the intake manifold. If you look into the manifold, you will see a round disk covering the opening. Crud and dirt tends to build up around the outside edge of the disk, and can cause stalling (and maybe poor fuel economy). You can easily clean this area with a little laquer thinner or mineral spirits on a Q-tip or rag. You will need to open the metal disk (throttle plate) to do a thorough cleaning. Just push the disk gently inward at the bottom of the disk, and it should open enough to get at the dirt. After performing this cleaning on my truck, the stalling and rough idle went away, and after 120k miles, has not returned.
I don't know if this will help your mileage, but it couldn't hurt.

I have a 2000 Tundra 4x4, ext cab,V8, and consistently get 16.5-17 MPG.

I had the intake flushed as well as the fuel system and put on a K&N intake and WHAT A DIFFERENCE... Picked up 1.5 mpg that I lost putting on a grill guard, tow hitch and step bars...Intake was WELL worth the $$'s

I have an '01 Tundra 4x4 TRD with the access cab, and I get 14.5 mpg EVERY tank. I drive equally as much on the highway as in the city, but it doesn't seem to matter where I drive, I'm cursed with that number 14.5. I'm looking into buying a K&N intake or air filter only. Anyone tried just replacing the filter with a good K&N?

K&N replacements help, or a new intake would really be best, like a cold air. but a new drop in filter, id always pull a couple plugs to check em out. can always put it back in if its fine ;)