Computational Thinking in Undergraduate Discrete Math and
Multimedia Logic is a open source FreeWare tool for experimenting with logic circuits.
An Introduction to Digital Logic - Signals and Gates is a nifty site for experimenting with logic circuits at Bucknell University.
Mastermind analysis at cuttheknot via the MAA.
What is lambda Calculus? UTexas knows a bit about it. How is Lambda related to Scheme? Even Australians study Lambda. NYU has a Lambda tutorial. UK guy has nice intro to Lambda. UPenn has great Lambda resources too.