Power5 instruction set

What different kinds of processors are based on the Power Architecture platform?
Power Architecture family members are stealthy chips, and they like to go by many different names. They can be hard to keep track of because they don't all use the PowerPC trademark. The well-known and ubiquitous Motorola PowerQUICC chips are PowerPC, though most chips made by Freescale (the new name for Motorola's chipmaking division) get names like MPCxxx. The famous Apple G5 is a PowerPC, as were the G4 and G3 before it; and even Nintendo's Gekko is based on PowerPC. And there are new ones created every day.
The chips in the POWER line are numbered 1 through 5, with POWER6 currently under development. POWER4 and POWER5 chips run servers on sale today. For more on the POWER line, see this excellent IBM SP Systems Overview writeup from the folks at Lawrence Livermore Labs, as well as Erik Klait's column on 27 years of IBM RISC.
In 1993, Apple, IBM, and Motorola banded together to form the so-called AIM alliance, which created and marketed the PowerPC family. IBM PowerPC chips are usually divided into three groups: the 6xx/7xx standalone family, the 9xx standalones, and the 4xx embedded family (note that assets associated with IBM's 400 series of embedded PowerPC standard products was recently acquired by AMCC). Information about Motorola PowerPC processors can be found at their daughter company, Freescale. Freescale makes the G4 chips for Apple; IBM makes the G5 (and made the now-discontinued G3).
For an in-depth look at how the PowerPC chips used by Apple have evolved, check out this excellent history from Ars Technica.
There are a number of specialized Power Architecture flavors in common industry use. For instance, Gekko, the processor that runs the Ninentendo GameCube, is a PowerPC variant manufactured by IBM. Xilinx and IBM worked together to create a hybrid chip family based on the PowerPC.