You can participate in the User Experience Research study by either visiting Google Offices, or filling an online survey or even from your home by testing out the Google product online and giving feedback to Google over phone. In some cases, Google Researchers may make come to your home itself to interview you about how you use computers or the Web.
You will get paid depending on the type of study, but typically Google pays $75 for each hour that you spend with a Google researcher, either in person or on the phone. Your travel expenses won't be reimbursed however. For online surveys, which you complete from your own computer, the amount varies, depending on the length of the survey.
Sign Up To participate in the Google user experience research study. Detailed information here. [via v7n.com]
Related: Work from Home for Google - all you need is a bachelor's degree and a high-speed internet connection to telecommute.