I will be there for a week. Gosh I miss Boston, being an East Coast native, and I'm glad for the visit.  Besides the obvious , what is there to do in the area to fill my day?

Its best to generalize the area  
Like * waltham to burlington *
Give you more cushion room for Safety and Security
 Keep in mind we are not the only ones that read this board

Actually, it's better to mention no municipalities at all.  

But, to fill your day, you could toodle over to the Old North Bridge in Concord, where the shot heard around the world was fired 241 years ago. That shot started the American Revolution, which resulted in the freedoms you enjoy today as a provider

Well saying you want to site see in Lexington doesn't mean you are staying there

As for stuff to do.a round Lexington...
Minuteman park for walking, running, biking
Some nice local shops in town
Daikenyama (sp?) for sushi
Nice little movie theat

Sounds like there is a lot of old charm that I'll enjoy just like the rest of the area.