I bought a 2001 trek 6500. I keep going through front tubes... and all i'm using it for the moment is commuting on pavement. The tire is a little warn out, but i have a hard time believing thats the problem. Could the tire be the wrong size for the rim? Or is that never the case. Its only a 26x2.1.

any help would be great. Thanks!

Where are the holes in the tubes?
Inside toward the rim or outside toward the road contact area?

What kind of flats and where are they? If single hole then they are either by a spoke head (if on the side against the rim) or possibly something stuck in the tire (if they occur in the same spot - make sure you line the tire's label up with the valve stem so you know what part of the tire is near the puncture site). If two small holes, could be low tire pressure. Could also be pinching the tube between the tire and rim when mounting.

What do you mean by worn out?
Where are the holes in the tube? Got pics of the tire? Have you checked the inside of the tire for glass, metal, etc protruding through?

As CACycling mentioned, the best diagnostic tool is to align the valve stem with the center of the tire label. This indexes the tire so you can easily correlate puncture location of the tube and tire. For example, if the tube is constantly being damaged on the tread side in a certain spot, then there could be a small wire or piece of glass embedded in the tire. A recent poster found that a wire from the bead was puncturing the tube (in this case, the tube damage was on the side of the tube which is unique). A puncture on the rim side of the tube could be caused by an exposed spoke thread, or a burr on the rim.

I guess we'll need more information to help out better.