You, too, can participate in reseach. And you don't even have to leave your keyboard. But, be careful about giving out personal information that can be linked to you as an individual — if in doubt, don't!
A few specific studies:
Inventory for the Assessment of Psychology
Kimberly Young's Internet Addiction Survey — Have you wondered about your online activity? You cannot get individual results here, but you can add to the base of knowledge and soon view the preliminary results of this ongoing study.
The APS and Yahoo sites offer the largest lists.
For a little research fun: