All under the sun ( :-)

Reviews
http://www.gabotronics.com/resources/hobbyists-oscilloscopes.htm
http://reviews.ebay.com/Buying-an-Oscilloscope-on-ebay_W0QQugidZ10000000001568756

Learn

http://www.opencircuits.com/Oscilloscope
http://www.picotech.com/applications/oscilloscope_tutorial.html

Cheap & Maybe good
http://www.bitscope.net/store/?p=view&i=item+1

Links
http://www.roboticsindia.com/showthread.php/3608-Best-Oscilloscope