maybe voxengo's span:



http://www.voxengo.com/product/SPAN/



for waveform visualisation this is really cool:

s(M)exoscope



http://bram.smartelectronix.com/plugins.php?id=4

http://bram.smartelectronix.com/scope_docs/


another freaky one:

Fre(a)koscope







http://mdsp.smartelectronix.com/ffttools/