I'm looking for a Metafilter post that was about a browser ... um, application? or plug-in? or site? that featured different windows so you could drag/arrange your pages into groups by arbitrary topic or category, or work vs. leisure browsing, or whatever you wanted. Do you remember that?
I think it was being beta-tested, and I really wanted to try it out, but my computer was not behaving well at that point and I was afraid it might send it over the edge. I have absolutely no idea when this appeared, but probably some time in the last two years.