I'll grab a few exercises from this Bruce Lee's exercises book I picked up...
1) Previously mentioned - wrist roller
2) Fingertip pushups: kind of self explanatory, but just replicate normal pushup procedure but use fingertips rather than palms. Probably more to help strengthen fingers though.
3) Reverse Curl: 'strengthens extensor muscles on the backs of the forearms. Grasping a barbell with an overhand grip, stand erect so that the barbell is resting in front of the thighs at arm's length. Keeping the upper arms motionless, bend the elbows and raise the barbell until the forearms are horizontal to the floor. Pause for 2 seconds and then continue the movement until the bar touches the chest. Pause for 2 seconds and then continue the movement until the bar touches the chest. Lower the barbell at the sam speed as during the upward movement, observing the pause when the forearms are horizontal to the floor. Inhale as the weight is raised, exhale as it is lowered.
4) Barbell Wrist Curl: You have to be seated for this (and the next) exercise. Hold a barbell and with your forearms resting on your thighs, palms facing up, lower and raise the barbell with wrist strength alone.
5) Reverse wrist curl: Basically the same as above, but with the palms facing downwards.
6) Isometric squeeze: Simple, just get something to grab (spring loaded grippers or even tennis ball) and squeeze it. Try to sustain the squeeze for 10-15 seconds.
There are a few rules pointed out as well.
Do a complete extension and contraction. Do all exercises at a reasonable speed to keep the muscles warm. Don't cheat on any of the exercises. Don't allow the weight to roll down the fingers-keep fingers closed and maintain a good grip on the bar at all times.
There are a few other exercises in the book, but think it's enough typing from me. It is quite a useful book in that it has a lot of exercises described by category, and also gives suggestions for how to go about the exercises depending on objectives (power, muscularity, size). It also has exercises routines and workouts, as well as diet tips and so forth. Quite a useful buy if you're into the workouts. Title is 'The Art of Expressing The Human Body' from the Bruce Lee library - volume 4. By John Little. Tuttle publishings.
http://www.amazon.com/exec/obidos/AS...647277-1471848
Good luck mate.