I think virtual desktops can be one tool that helps if you are at a computer a great amount of the time. If so, you can simply switch to a different desktop to address your interruption.
Another tool that can be helpful is Relaunch ($5). It snapshots your window positions and even your open documents (in some popular programs). Though it has utility beyond just interruption switching, the ability to manage interruptions by snapshoting what you were working on and opening a snapshot for another task/project quickly can be a big help.
http://wiredupandfiredup.co.uk/Relaunch/