Do you reside in the US or Canada? Do you want to improve Google Maps? Google is looking for volunteers for a study which would involve you either going to Google's offices (if you're able), performing a study online, having a Google rep visit you, or by filling out an online survey. The actual study itself isn't exactly explained, but if you're interested, the URL to register and be considered for participation is:
Google says that qualified participants may be able to earn up to $100.
If you've taken the initial survey like this before, it's relatively long. Google asks about your usage of software products, business habits, and more. It should take 10-20 minutes. But in the end, you may end up getting an extra $100 if Google likes you enough to pick you from the crowd. :)
Forum discussion continues at Google Groups.