GPU overclocking tools

With these tools it is possible to change the clock speeds of Radeon graphic cards to increase hashrate and thus mining profitability.

Usually core clock is increased and memory clock is decreased to lower temperatures and save power.

Windows

AMD GPU clock tool - GUI / command line, http://www.techpowerup.com/downloads/1128/AMD_GPU_Clock_Tool_v0.9.8.html
AMD / ATI Tray Tools - GUI, http://www.guru3d.com/article/ati-tray-tools-/
ClockTweak - command line, not free, multiple cards, http://forum.bitcoin.org/index.php?topic=9982.0
EVGA Precision - Nice GUI, multiple cards supported (can use others than EVGA cards), supports multi-CPU setups, change clock settings for memory and other setting, new integrated GPU Voltage Tuner, http://www.evga.com/precision/
MSI Afterburner - fancy GUI, multiple cards, needs to be unlocked, some problems with multi GPU setups http://event.msi.com/vga/afterburner/
RBE Radeon BIOS editor - GUI, can also be used to overclock, http://www.techpowerup.com/rbe/
Sapphire TriXX - GUI, Works very well for multi GPU setups with or with or without crossfire. http://www.sapphiretech.com/ssc/TriXX/

...