You have no credit cards that offer cash advances?
I suppose you could always volunteer your body to science – in Boston, there are usually various places offering money to serve in trials or psych studies. However, your two day deadline is fairly tight.
Are there any job fair situations where you could get a “clean up the yard for $10.00/hour” type of job?
I won’t mention the links at the bottom of the thread 
My fiance and I have both found “day jobs” at various parking lots in Memphis.
Remisser I like the CraigsList idea. Also look at selling blood plasma, donating sperm (are you a guy?), or taking part in a medical experiment (look in the want ads). There are also day labor sites.
But, more importantly, I am from Wollaston originally. How is Quincy these days? I miss Brighams and the pizza. My old neighborhood now has all these cool Chinese stores and restaurants. The old A&P now is the 88 market and sells two different kinds of live eels.
That would be my advice. My credit union card doesn’t charge a cash advance fee or higher interest rate for cash advances, either.
These can be fun. The one’s I’ve seen are a slightly more organized version of the old-school, show-up-at-4 am and wait for somebody standing on the back of a truck to point at you. Look in the yellow pages for names like “Labor Ready” or similar. Show up as early as possible – meaning, be the first guy there. You’ll likely be at hard labor, and would possibly need to borrow a small amount to cover your $100 after two days (well, one day, on account of the timing of your post).
Just pawn something. Pawn your computer monitor, router, printer, any musical instruments, any stereo equipment. If you can play music, busk on the street if you live in the kind of town where you could. Use your credit card if you have one. If you have any cash or check, look for a bank running a promo offering a cash reward for signing up for a checking account (I’ve seen several advertising $100 just for signing up). Get a job distributing flyers for some dirtbag free newspaper. If these options don’t work, you’ve got no choice but to gamble whatever capital you have. I’d hit the OTB, armed with as much information as possible, before I went to partypoker or sim., but that’s just me.
Check out the Craig’s List “gigs” section. Sometimes you can find one night jobs that pay around that.