Escher via LEGO
Balcony
Belvedere
Ascending
(Many many thanks to Mike)

Fenris is a set of tools that include a high-level tracer, library fingerprinter, debugger, and a data exploration interface
Design and learn access controls in networks, systems and applications with Access Road
Memphis can be used for the definition of abstract syntax trees and the implementation of tree walkers.
Use Cqual to add type qualifiers to C
...and Mpatrol to diagnose run-time errors that are caused by the wrong use of dynamically allocated memory