Huge cheat-sheet about matrices and formula associated.
All you ever wanted to know about regular expressions (especially useful combined with Sed).
Will do wonders whether you need to filter data from a file, rename files/folders, etc. Think about filtering, think of Sed!
Reminder about rotation conversions, with code associated.
Y! Pipes is a graphical interface for PERL code, oriented towards feed manipulation. The resulting simplicity enables one to do create fast and simple web applications, but also complex ones, especially with YQL-execute to add a server-side javascript step.
Y! YQL is mainly an interface aggregating APIs and providing an SQL-like access to those. More importantly (in my opinion) is YQL-execute, allowing one to store and execute JavaScript on Yahoo's servers, and even interface it with Pipes (both ways).
The blog (in French) of a friend, in which he writes about advanced LaTeX, Linux and miscellaneous geek stuff.