Has anyone found the cure for "work boredom" yet?

I work as a secretary at an accountants office. Tax season is over so i pretty much do nothing here but answer the phone and greet clients that come in the door plus a few little other secretary duties but i finish everything so early in the day that i just sit here on the computer for 7 hours. I dont want my boss to think im just sitting here doing nothing all the time. I clean, i ask for stuff to do but nothing. Now dont get me wrong, i LOVE my job :) But a person can take just sitting for so long. Any ideas of something i could do to make myself look busy? lol