I am addicted to screen real estate. So much so that even a 15" laptop screen isn't enough to hold it all. At my desk I have a 20" Cinema Display next to my MacBook Pro. When traveling, though, I have to make do.
I do always have my iPad with me. If only there was a way to...
Ta da! Enter Air Display! If you're on wifi (and where aren't you these days?) you can use your iPad as you would any old second monitor. You can mirror your main screen (okay, I haven't found a use for that yet, but you can) or you can just add another 768x1024 to your desktop for some ancillary application or reduce your window congestion in a development environment like, ahem, FileMaker. Behold:
I'd much rather have my Cinema Display for this kind of work all the time, but it stretches the seams something fierce on my laptop bag.
Air Display is $9.99 in the iOS app store and works on the iPhone, iPod Touch and iPad.