You can purchase replacement hinge pin and bushing kits from Napa, O'Reilly, Etc. Part numbers are: Dorman 38422 NAPA 675-1594 They are about $5.99 per pin, (2) required per door.
Then you have to install as listed below on digitalrevo.
There is a hinge kit available from dealers- my understanding is that it's pretty expensive, and replaces the complete hinge, so it requires welding a new hinge to the door. My door was rusted out at the bottom anyway, so I bought a complete replacement from a salvage shop.
Here's a guide to replace the door pins and bushings. http://www.digitalrevo.com/jeep/doorpins.html
Digitalrevo is not an active website as of 12/24/07