We have done this for Lent for a couple of years now and the kids enjoy it.
For every "good deed" they do, they put one bean in the jar. It is also a way to reward good behavior. It has been a BIG DEAL here the past couple of days to be able to put a bean in the jar!
During Lent the beans pile up and on Easter Sunday...jelly beans replace the good deed beans! It is always a big "surprise" on Easter morning.
(Although last year no one really seemed to like the jelly beans, so Ryan and I ended up eating them. And then we always end up pitching all of the black jelly beans that no one likes!)