This game was also at optimumtennis.net but was a little hard to decode so I hope I am explaining it
right. If not, at least I understand my own explanation. :) They did not give it a name so I took the liberty. I like it for its flexibility and requirement for players to hustle. You will need 2 or more players for this to be any fun.
Coach is on one end of court; all other players on the other. First player serves, then hustles up net diagonally from wherever they served. Meanwhile second player hops in to first player's spot at baseline. This must occur quickly because Coach will be returning the serve cross court to the second player. Player 2 returns Coach's shot. Coach then hits to net player. Coach continues alternating shots until point ends. Player 2 then serves and runs up to net diagonally that Player 1 has just vacated, and Player 3 steps into Player 2's spot.
This game should move quickly. If you want to add a scoring aspect, give all players a set number of points and subtract one for every error. Last player standing, wins.
UPDATE: Sorry to report this was an epic fail when I tried it with my intermediate green ball class. They could not get in a rhythm. Serving player on way to net kept wanting to hit the ball I was returning deep to second player. Oh, well. Maybe try again in future.