I run my Mac with Japanese set as the default langauge. However, sometimes I want to run programs in English, and it was always a pain to go to System Preferences -> International and change the language. I know I can also deselect Japanese from the Language section on the Get Info window for each program, but then I would have to turn it back on later. I discovered a way to change the language from the Terminal that makes things a lot easier.
When I'm in Japanese mode and I want to switch to English, I run the following command:
defaults write NSGlobalDomain AppleLanguages
"(en, ja, fr, de, es, it, nl, sv, nb, da, fi, pt, zh-Hans, zh-Hant, ko)"
Once that is run, any program that you launch will run in English. To switch back, just swap the two languages you want, like so:
defaults write NSGlobalDomain AppleLanguages
"(ja, en, fr, de, es, it, nl, sv, nb, da, fi, pt, zh-Hans, zh-Hant, ko)"
Using this basic idea, one can temporarily switch into whatever language they want and not have to hassle with System Preferences. I wrote a simple AppleScript droplet that I can drop applications onto, and they will run in English. I'm sure the code could be simplified, but it gets the job done in its current form.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20061229203902170