"How-Tos" for Rolling Your Own Short URLs?
ivankirigin: I made one for Tipjoy where I mapped a content ID to short string, and loaded a frame like the Digg Bar where people could donate to the site and view the content. For example: http://tipjoy.com/2w/Here is the python code I used to "shrink" and unshrink the content ID.  def shrink( id ):
      validCharacters = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ._-~"
      base = len(validCharacters)
      characterArray = ""
      d = id
      while d > 0:
          ind = d % base
          characterArray = validCharacters[ind] + characterArray
          d = d / base
      return characterArray
  
  def unshrink( code ):
      validCharacters = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ._-~"
      base = len(validCharacters)
      val = 0
      revCode = code[::-1]
      power = 0
      for r in revCode:
          i = validCharacters.find(r)
          if i==-1:
              raise
          val += i * (base**power)
          power += 1
      return val

If you think this code is bad for some reason, please tell me in the comments. I spent little time reviewing it when I wrote it about a year ago.