My roommate and I rented out our living room and attic :P Not tolerable to most people, but we're all broke... three of us are also on my (discounted) phone plan, so we have iPhones for half the normal bill. Buy in bulk as much as you can.
I budget US$5 of "whatever" a day (coffee, food, beer), US$40/week on groceries and cook meals, and use Mint.com to keep track of it all. My credit card has frequent flier miles, so I put almost everything on my credit card and pay it off in full before it's due. This always keeps me accountable for every penny I spend, because I can see it on Mint.. as opposed to cash, which isn't as trackable unless you want to collect a bizillion receipts. I've racked up enough miles to save US$2000 on flights during my trip.
I also do as much under-the-table work as possible, e.g. dog-sitting, housecleaning, etc. It makes me effectively more per hour than my full-time job. I put that money towards pre-trip supplies.
I also have a piggy bank like #gawkabout's - I bought a laminated wall map to plot routes on, and used the tube it came in as a travel bank... pasted map pictures, random tickets, money and entrance passes from former trips on it, and dump all my change in it. There's some $5's and $10's in there too :P
Act like a poor person, get rich.