There used to be a good one here: http://www7.brinkster.com/obyrne/rhp_rc.htm but it hasn't been working for a while. Does anyone know of a similar calculator?
Firefox + Greasemonkey + http://members.shaw.ca/ouroboros/RHP/rhp.user.js = "Adds the amount of ratings adjustment for a win/loss/draw beside each player's rating."