The trolley tour of Boston, offered as an optional, is the best way to see the entire city. Take it at your own pace, but I would suggest stopping off at the USS Constitution and Fenway.

ankopsu Article on Boston

I went on two tours alone...I made life-long friends along the way! That's the nature of Contiki.

efti Article on Travelling alone

If you are doing a time out tour (staying in hotels), a travel iron/hairdryer will come in handy as many european hotels do not provide these facilities.

Vicki - Contiki Staff, Europe Article on Suggested packing list - Europe - Summer