Starting in 2006, Apple started changing the naming conventions of some of their machines when moving to the Intel processor. As has been obvious from these boards some are confusing the new iMacs and Mac Minis for G5s and G4s respectively. Here are the actual naming conventions, and how to identify them:
iMac G5 was followed by the iMac Intel Core Duo, and then was followed by an iMac Intel Core2 Duo. See this article on identifying it:
eMac followed by mid-2006 Educational iMac
Mac Mini (G4 with 2 USB ports) Mac Mini Intel Core Solo and Duo (with 4 USB ports)
iBook followed by MacBook (name beneath the screen)
Powerbook followed by MacBook Pro (name beneath the screen).
PowerMac G5 followed by MacPro (both have cheesegrater cases, the later has two optical drive ports).
Some of the G5 and G4 models listed above sold well into 2006, but once the name changed to the model listed above they were no longer G5 and G4.