Guiminer

For those using Windows Vista or Windows 7, I think that the easiest to use mining software will be that of the Guiminer.   It has a very simple graphic interface with extensions and commands for those who are more experienced.   You basically can't go wrong with using this as it is just click and play with a lot of the more popular mining pools' configuration already inbuilt.   Strongly recommended for those who are just starting out.