What could cause tail light fuse to keep blowing? Just had a new alternator installed. Not sure why fuse keeps blowing.

 

Most likely a short, check all the wiring in the trunk.

 

Sure enough that was my problem!!!
My fuse kept blowing and it was driving me crazy.
Tail lights stopped working along with front side headlights.
I checked the wiring under my trunk and sure enough the wiring had cut and was rubbing against the trunk causing my short. I wrapped the wire put in a new fuse and BINGO problem solved.

 

Does your car have rear headlights??

Fuses blowing are almost always a short circuit/short to ground as Flava said.