I know. I've being thinking about how to do it, currently it involves having N hashs where you generate them like:

  echo -n "password" | md5sum
  5f4dcc3b5aa765d61d8327deb882cf99  -
  echo -n "assword" | md5sum
  297dbe7699dcfa60609bf9e667e2e4dc  -
  echo -n "pssword" | md5sum
  537319a7934aea9825d1af85df588fde  -
  echo -n "pasword" | md5sum
  22e5ab5743ea52caf34abcc02c0f161d  -
  echo -n "pasword" | md5sum
  22e5ab5743ea52caf34abcc02c0f161d  -

ect, then check the submitted password by testing it against these hashes by removing characters in the same fashion.

Just as an early idea.

I think it's a good idea, what if you could encourage users to use stronger passwords by telling them that "the system will forgive near misses, so don't be afraid"?