I have similar question, too. I play tennis once or twice a week and I'd like to improve my performance.
Yesterday, I ordered a tennis instruction video, "Nick Bollettieri Tape Series : Killer Forehand",... and still waiting for its delivery.
I heard that it has some good reputation,.. and heard that Srichapan (spell?) watched the video many times to have better forehand stroke.
I think you can order tennis instruction video in many places such as Amazon.com.
This is the link in Amazon.com for tennis instruction Video.
Hope it's helpeful for you.
If I receive the video tape,.. I'm post some info for you here.
Good luck to your video lessons.
PS. Just ignore nasty reply.