You can, it's really easy and here how. It's like a soft reset as opposed to a hard reset.
Have you ever used an app on your iDevice and the screen just seems to be taking longer than usual? Well here's how to refresh the memory without rebooting. Try this first before you do a total shut off, to reboot the iDevice which would be a hard reset.
When your iDevice appears to be locked up, press the Sleep Button until the drop down screen pops up informing you to "Slide to power off" and the "Cancel" button at the bottom. Now press and hold the HOME button until the iDevice goes back to the app screen, then release it and launch the app again and it should work normally. If for some reason it doesn't then you may have to do a hard reset by turning it off with the Sleep Button and then back on again.
I don't have a iPad to see if this works or not, so if you do, let us know in the Comments if it works for you so the other readers will know also.
I just got a twitter from my friend ram8727 who informed me that this procedure worked for him on his iPhone 4 since it locked up while he was using Safari. Very Cool