Keynote
Keynote (formerly Vividence) is a tool that allows large-scale, interactive and remote user-experience evaluations on any live website, and which collects qualitative and quantitative self-report and behavioral data as users attempt assigned or self-defined tasks.
Keynote studies are appropriate when the context of use is central to the tasks under investigation, because Keynote allows users to participate using their own computers, at home or at work.
Keynote studies are useful when large sample sizes are needed to generate statistically significant differences between experience measures pre- and post-task, between competitors, or at different points in time.
While real users are involved, Keynote studies generate information about what the state of the user experience is and less about what contributes to it; they are therefore best used as a complement to small-sample studies such as usability testing.
There are licence costs associated with using Keynote; visit http://www.keynote.com/ for more information.