I've been using the excel tools at:

http://www.fourmilab.ch/hackdiet/www/hackdiet.html

to let me track weight lost.  I've put today's snapshot up on
my blog (moved to livejournal from blogspot):

http://www.livejournal.com/users/atkinsandme/

I like this ten day rolling average approach because it lets me see
progress even during plateaux (and also keeps me from getting
too cocky on days when I lose 3 or 4 lbs).

.