The design goal was to build a fairly simple device which allows to digitize signals with frequencies ranging from DC to around 1MHz with very long sampling buffer (i.e. millions of points).
http://www.triplespark.net/elec/analysis/USB-LiveOsci/
An ordinary TV has been turned into a digital storage oscilloscope with a sampling rate of 160 ksps. This article explains how to use an LPC2138 microcontroller to build a high-resolution system of your own.
http://www.circuitcellar.com/library/print/1106/Momontov-196/index.htm
Miniature TV converted to simple oscilloscope - Notes on converting that old compact tv set or computer monitor into an oscilloscope. Proves very useful in line quality monitoring and other low frequency applications.
http://www.dansworkshop.com/Homebuilt%20oscilloscope.shtml
Oscilloscope Block Diagram and Schematics by N4BCU
http://members.tripod.com/michaelgellis/scope.html
put many traces on a single input oscilloscope.
http://www.intio.or.jp/jf10zl/mulv.htm
This is a simple PC voltage oscilloscope using only a PIC12F675, a 20MHz oscillator, and a RS232 level shifter.
http://www.semifluid.com/PIC12F675_Oscilloscope.html
The microcontroller used is a Microchip PIC18F2550. The PIC18F2550 runs at 48MHz using the internal PLL. R1 is a pull-up resistor necessary for operation.
http://www.semifluid.com/?p=23
A simple and effective USB oscilloscope using the higher performance PIC18F2550. Using HID means that this oscilloscope does not require drivers (only the oscilloscope software).
http://www.semifluid.com/?p=24
uses a matrix of 100 LEDs for a display
http://www.geocities.com/SiliconValley/Lakes/7156/articl3.htm
What is an oscilloscope, what can you do with it, and how does it work? This section answers these fundamental questions.
http://www.cs.tcd.ie/courses/baict/bac/jf/labs/scope/oscilloscope.html