Accidentally deleted /usr/share directory... what can I do to fix it?
Tough break.  If you have never backed up with Time Machine, then you should look at this link for a post on free undelete utilities.  Or you can ask a colleague to compress their /usr/share folder if you're desperate.  Last suggestion would be setting up a VM with your OSX version and copying it from there, but if you don't have Fusion or Parallels already installed, they'll ask for a reboot.

Good luck.