CPU Speed Menu for Mac

From Marcel Bresink Software-Systeme:

CPU Speed Menu allows you to switch between the different performance settings of your computer by a single mouse click. It is no longer necessary to open System Preferences, navigating to the Energy Saver pane and selecting the Options item. This is helpful for users who must switch between different speed settings very often, for example when temporarily performing processor-intensive tasks. Switching manually to a speed which meets your current needs best can improve battery load on portable computers, or avoid noise problems with cooling fans and power supply units on desktop computers.

CPU Speed Menu can be used on all Macintosh computers which support manual switching of processor performance. This includes all portable computers with PPC processors, as well as most G5 systems.