This quick look at Reaction Grid is the first in a series of one minute fly-throughs of alternative Virtual Worlds. Although their web site is in desparate need of an Information Designer, it has a great deal of information once you wade through the menus. Here are some quick links:
Free User Account Registration
Log in Instructions
Reaction Grid is a serious player in the OpenSim grid space, with a focus on education, enterprise and consumer markets. A number of high profile Second Life residents and organizations have projects on the grid including Wizard Gynoid, iLIVEsl and Jokaydia, as well as Microsoft.
This video is just a fast fly-over intended primarily to tempt SLers who haven't yet made it off-world to another grid to give it a try. For a more detailed tour, check out this post from Shockwave Plasma.