See memory usage of open processes in OS X at a glance

Memory Usage Getter is a program which graphically shows the memory usage of open processes and applications in an easy-to-use interface that provides useful information, not cryptic data, through the use of visual representations as well as a table showing you all the information you want to know. Version 2.2 includes several new features, including the ability to kill processes from within MUG, a true Cocoa toolbar, and French and Spanish localizations. More info here.