I am planning to use my laptop during travelling where it will connect to internet through costly and slow mobile connection, as well as my regular in use computer where it connects through the high speed broadband.

In the latter case I want several of the applications (eg Dropbox, newsreader, Gmail checker, ubuntu updates etc.) to connect to network without requiring my starting them manually (I have them set to start automatically), while in latter situation, only the app I want should connect to the network (usually a browser). I don't want to manually shut down dozen of these (which basically I won't even remember).

Is there an application (should be called an "application firewall"?) that allows me to set a profile in use, and blocks are allows certain applications to connect to network depending on the choice?

(Firestater, seems to have no option for application based filtering, I just checked. Correct me if I am wrong).