The best GPU mining software is DiabloMiner. The software is compatible with GPU mining and offers large access to group pools, which is rare in the market. The only snag here is that DiabloMiner uses a command line interface, which is not appealing and might be difficult for users without technical experience. An alternative to DiabloMiner is the Kryptex software which has a GUI and is more flexible to use, but the software doesn't come cheap.