Holy crap, the back tagging project (recent update) is complete! 43,000 old posts have been keyworded by a team of hundreds of volunteers here. A huge thanks to all, I never thought we'd finish up all those old MeFi posts. [more inside]
I'm testing out tag search on MeFi. Here's a search for "goo" and one for "music" showing typical results. It can be reached on the search page. Post any bugs or further suggestions inside.
I'm in the process of adding keyword tags to MetaFilter. Right now, you can go back and tag all your old posts. Please, help me make this a useful feature by tagging your stuff with descriptive keywords that help people find other related posts. We could really turn this into something useful if we stick to that. I'm still working it into the new post form and working bugs out of the display end, but the basics are now there. Go forth and help make this useful.