Check out the Javelin Thrower's Forum at the following URL:
http://disc.server.com/Indices/109718.html
On the left side, there are a number of links for technique and training. The one called "Exercise & Muscle Directory" shows low-res videos of a number of great training exercises for both upper and lower body. Another one, "Kari Exercise Photos" is a little more advanced drill.
Actually, the best work for building upper body and muscle memore is to swing sledge hammers of different weights. Go to the link "Sledgen Drills" and it will take you to some YouTube videos of some hammer swinging drills (of course, you will have to come up with some kind of tire setup in order to do these).
Good luck, throw far.