Useful web pages
The French yellow pages by France Telecom;
Informations, fares, and reservations for the SNCF, the French railways company;
Google: my former favorite search engine, for all its related apps;
Duck Duck Go: my new favorite (meta-)search engine, very customizable and nicely integrating heterogeneous results.
Mac and Mac OS X
Though I am mostly using Macs, I use quite few Apple applications. Terminal, iCal-Address Book-iSync, iPhoto, sometimes iTunes...
Debian is my preferred Linux distribution, for philosophical as well as practical reasons (package management, administration scripts, security updates, etc...);
I used to be from times to times under OpenBSD, the best platform for security;
my graphical environment under Linux is quite minimal, I thus chose lightness with Window Maker (I was for a long time a satisfied user of fluxbox but eventually gave in to the temptation of eye candy, I must be getting old) enhanced by a multi-function monitor: torsmo which replaced my good old GKrellM.
I mostly use LaTeX when it comes to producing documents, and for some time I've been very happy with the beamer class (which can be seen as successor of prosper) for slides (especially for video-projection);
Besides GNU Prolog and C, the language I mostly use, especially for scripts, is Python, which replaced Perl and its wonderful CPAN archive with its package index. I must admit to also write some shell-scripts, which is made quite easy thanks to bash;