Ubuntu Software Center got a really cool feature in Ubuntu 11.04: it lets you test drive applications without having to install them.
To get this to work you firstly must install a package called "qtnx":
sudo apt-get install qtnx
Then when you open Ubuntu Software Center you should see a new "Test drive" button next to the application screenshot. The applications run on a remote server so you must have a decent Internet connection and also, this is not available for all the applications in the Ubuntu Software Center, but nevertheless, this feature sounds awesome. Here's a video I've just recorded so you can see exactly how it works:
Thanks to Novatillasku for the news!