Here is some info that might help you out in your travels. I did this ones and it was a pain in the rumpus. You see if you don't know what to expect and you are a cheap person like myself because you realize that.
OK where do you get big stuff?
You find it on the curb on garbage day, this "seems" to be all available to steeling.
You can also go to some of the big box stores if you have a vehicle to drag somthing home. some of these includeStaples, Walmart (evil as it might be).
You must remeber that you are in a place where people "have money" or atleast a good portion do and so the idea of a "thrift" store is a bit out of the question. You see with realastate being in the position that it is, it is hard to find space to sell "garbage" to scroungers such as myself and possibly yourself.
Transportation
Boston has a grand public transportation system, in fact sometimes I think that you could get to the moon if you could find the right bus/subway(T) combination. The subways is called the "T" don't ask because I don't know why. And it extends out above surface away from the city for quite some distance.
The city of boston transportation athority has a great website, www.mbta.com. Where you can find out all about it. You pay when you get on the T or the bus and then you go where you want to go. Pretty simple all in all. With the website you can give it two addresses and a departure time and it will give you directions including where and when to get on the public transportation.
note: in the winter time you need to dress warm and be ready for a good hour waite in freakin cold weather and wind.. and you will feel kinda stupid standing by the bus sign waiting for the bus which is rarly there when it should be. (just be sure and note that, not that I havn't done it a time or two.)
Also an interesting place for grabbing computer parts if you are there is MircoCenter.
One of the great things I have discovered is the Hay Market, Which
happens every Friday and Saturday from "dusk till dawn". You can find
everything from fish to vegetables there. Most all of it is cheap as
dirt, but remeber "sometimes" you get what you pay for. If anything it
is a heck of a good adventure. To get there you get off on the Haymarket
exit on the Green/Orange line.