If you use Chrome, you're in luck. I developed the JunkFill Chrome extension for just that purpose, something to get me quickly through testing web forms. There are other extensions that have similar or better functionality. For most, you need to configure them and save the data so they can to fill out the forms properly for you.
JunkFill isn't about being proper, it's about being quick. It works right out of the box, so to speak, no configuration necessary. You can download it from the Chrome Extension Gallery. Give it a click and see how it works out for you.
