You probably know all these, but anyway: Momondo, Expedia, Travelocity, and Hotels.com are good for hunting for good travel&accommodation deals, Kayak and Flights.Google are excellent flight price comparison websites, JetBlue often offers promotions for flights on their page, WOW Airlines offer really cheap connections to Europe, TriPadvisor is great for eliminating bad hotels by travelers’ reviews, and AirBnB is a great alternative to hotels.
If you have more time than money, check Priceline for air travel: you can negotiate the flight price (and get it as low as to 60% of what you would pay), but once you make an offer and it is accepted, they immediately charge your card (and if they decline, you can’t make another reservation with them for the same day, so don’t start with 1$). In a sort of similar vein, HotWire lets you book hotel rooms really cheap, but you can only choose the area and hotel class. Hot is an interesting new startup, which offers last-minute discount accommodation in hotels.
Getting to NY
New York is a must and it is very close. Airfare and train are expensive, but there is a plethora of really cheap bus rides at Bolt Bus, Mega Bus, Lucky Star Bus, Go Buses, and even PeterPan/Greyhound sometimes offer cheap rides online. Go Buses leaves conveniently from Alewife. All other buses leave from South Station. Just check where the final stop in NY is, since it varies and may be sensible to know when making a decision. Most buses have free, slow Wi-fi onboard.