Form:
Working on dropping to your knees from your catching stance into a solid blocking position. Make sure you throwing hand is tucked behind your glove, and your glove is in between your legs, plams must be up or facing the pitcher. Chin down and a slight arch in the back, this will help absorb the initial impact of the baseball with your chest protector and direct the baseball into the ground. Work on form for blocking balls down the middle (just drop), left (jab step left foot, square and drop) and right (jab step right foot, square and drop). Go slow and controled, concentrate on form!!!
Once you have that mastered...
Block and Pounce:
Get in your catching stance as you would be before you recieve the baseball, drop to your knees and pop back up as quick as you can. Incorporate blocking balls from the left and from the right. Try to always square your shoulders to the baseball (like you would to direct the ball back to the middle of the baseball diamond.) Concentrate on proper form, but also quickness.
Do 5 sets of 5-10 reps or so. Once you get that down you can expand on it by place a baseball about 4-5 feet in front of you, block, pop up, and pounce on the baseball, make a throw or simulated throw.
The idea is to get quick and comfortable with the movement.
Unfortunately, there are not many other drills I am aware of that can be done alone. Given the nature of working out a cathcer you usually need someone willing to throw. If I think of any others I will let you know.