• Download the plugin Remove '/blog' slug plugin for wordpress Mu if you have yet not downloaded it.
  • Install it as any other plugin. You may upload to wp-content/plugins or just use plugin installer to upload and install it.
  • Go to Dashboard->Plugins(Installed plugins)
  • Activate “Remove /blog slug plugin for wpmu”
  • Go to Settings->Permalink
  • Copy your current permalink and then change something in permalink, save it. Now put your old permalink and save again.(See, you have to save it twice, we are just forcing wordpress to update the permalink structure by changing it, if you don’t change, the permalink is not saved, so It will not work. To get over it, we change it to something else, then save and then revert back to the original structure)
  • Go and check your posts now,they will have no “/blog/” slug anymore.

I have tested it with wordpress Mu 2.8.6, but I hope it should work fine with other versions too. I even tested it on a buddypress+wpmu installation and it just works fine.