Balking, Reneging, and Retrials

These three things make life more complicated (or should we say fun?) for queueing theorists. They are defined as follows:
When notified that they will have to wait in line, someone leaves the system instead.
Someone gets tired of waiting, and leaves the system before starting service.
Someone who left the system early (due to a busy signal, or balking, or reneging) tries again.
The following are links to software that deals with some of these complications. I haven't formally evaluated them yet.