began sending out notifications today to current Apps Free account holders informing them that as of May 10th 2011, the free account user limit is being reduced from 50 to 10 users.

The email goes on to say that this change will not affect existing account holders and that the 50 user limit will continue to be honored. However, new accounts created after the deadline will be subject to the new lower restriction.

I can confirm that I was able to register a new domain with Google Apps today and was still given the higher 50 user limit, so get in now and set up those domains while you can.