NOTICE: Waves has not been updated in a long time. Have a look at Timing Diagrammer for a new implementation of Waves.
Waves is a simple timing diagram editor written in Tcl/Tk that saves waveform information as a text file. A Windows binary (made with starkit) is availble, and the source can be run using wish if Tcl/Tk is installed on most OSs.
See here for a detailed document.