Is there any software or a procedure that would allow me to
- log out of all services (gmail, dropbox etc.)
- and/or delete any sensitive data remotely
...from a machine that has been stolen?
Find my Mac is free and part of iCloud. Included features are:
You need a Mac computer with Lion to use this feature.
Changing the password will log all devices out and force them to prompt for a new password. For things like web-based gmail, this stops them accessing your email.
Unfortunately, for things like Dropbox where the data is already on your computer it won't delete it - although you could use find my mac just to wipe the entire computer (provided it has an internet connection) and start again.
You can take a look at their recover stories.
A detailed description of how it works can be found on their website.
You may note that this software will not immediately wipe your hard drive. This is very important, because your computer needs to be online for localization. This software acts in the background making a potential thief feel safe in using your computer. You can still see what a thief is doing by watching transmitted screenshots.