WaveForms is a powerful suite of virtual instruments that brings analog and digital circuit design to your PC desktop. WaveForms seamlessly connects to our Analog Design products, such as the Electronics Explorer™ board and the Analog Discovery™ Kit. WaveForms provides a clean, easy to use graphical interface for each instrument, making it easy to acquire, store, analyze, produce, and reuse analog and digital signals.

Waveforms is free to download, and is available for Windows, Mac and Linux (although it is only installed on Windows machines at CAE).
http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,66,849&Prod=WAVEFORMS&CFID=6529835&CFTOKEN=de25659007ebda6-1165B989-5056-0201-023471C06D655FCE