Plan To Stay in Boston

Hello. I plan to stay in Boston. I would like to know the best places to "outlet" to go shopping at the lowest price for clothes and cheap car rental service in boston. I found these site : http://www.bostonstore.com/ ,http://www.toptenofboston.com/shopping.html , http://www.avis.com ,
http://www.bostonairportcars.com/

Please suggest me which one is best
Thank you!