MacRumors.com

According to a user submission, Apple has started shipping 1.5Ghz G4 Mac minis while still packaged in 1.42Ghz boxes. The system profiler shows the video card as a 64MB VRAM Radeon 9200, and a Dual-Layer 8x SuperDrive.

Mac mini upgrades were recently rumored in this page 2 post. The Apple online store still lists the Mac mini as being offered with either a 1.25Ghz or 1.42Ghz PowerPC G4.

Update: ThinkSecret is now publishing corroborating evidence.