If you like italian food, the North End has some great places to eat. Granted, it's not always cheap but it's worth trying it out. And I don't say this lightly because I spent the better half of my childhood in Italy
Oh and I totally second Fuzzy's suggestion. Def. check out the Arboretum - a little out of the way but beautiful this time of year. Renting bikes and riding up there from Boston is fun too