These guys have a great product and might really give LitmusApp a run for their money. But it’s no longer free.
“5% paid number in a freemium model is a great percentage traditionally, it only works if you have thousands upon thousands of users (ie Flickr, etc) – it does not work in an industry such as the web design area with a focused audience where we see hundreds of users per day.”
NEW: Bookmarklet. I’ve been using theLitmusApp bookmarlet for a while and it’s great. but this allows you to jump right into using a virtual environment OR taking screenshots.
What is really cool about the whole thing is how it can change your workflow in testing. You can work on a site and get it to your liking and two clicks later you can look at that site in IE6, Opera or Chrome. You can even run screenshots.