SRC332 Serve and Stay*
There are many options to use with this drill.  You can practice a certain shot pattern, for example serving down the center and then hitting to the open court.  In a group situation have two players rotating in to return serve and the other players serving.  Keep score; return players verses serving players and then switch with two new players going to the return side.

Here's another option; X1 will return serve and the other players will serve. The servers only have one serve. If a server wins the point they stay and serve again. Players keep tract of their individual scores to reach a designated number. The players will then switch with a new player returning serve.

Variations:

Players must hit a certain type of serve (spin or placement)

The player returning can only hit a certain type of shot (slice, topspin, forehand, etc)