http://developer.37signals.com/backpack/calendar/ (linked to from http://developer.37signals.com/) is missing.

I also had problems with the Ruby wrapper backpack_calendar.rb, which is also missing. I fixed some more typecasting problems and changed /calendars.xml to /ws/calendars.

Is the API in the middle of renovations or has it been forgotten?

Here’s the patched-up version of backpack_calendar.rb:
http://pastie.caboo.se/189985