AIRLINES
JetBlue Airlines
@JetBlue
Insider tips and problem resolution
@JetBlueCheeps
Deals on last-minute flights, offered every Monday
United Airlines
@UnitedAirlines
Flash airfare sales
Virgin America
@VirginAmerica
Deals, useful tips, and problem resolution

CAR RENTALS
Hertz
@ConnectbyHertz
Discounts, useful tips, and customer service

DISCOUNTERS
Hotwire travel-ticker
@travel_ticker
Handpicked selection of remarkable travel deals
Pleasant Holidays
@PleasantHoliday
Steeply discounted last-minute packages to Hawaii
Priceline
@TheNegotiator
Last-minute flight, hotel, and car rental deals
Quikbook
@Quikbook
Assistance in finding the best discounted rates at small hotels
Travelzoo
@Travelzoo
Steep last-minute deals, posted daily

HOTELS
Fairmont Hotels
@fairmonthotels
Twitter-only deals; contests with travel prizes
Hyatt Hotels
@HyattConcierge
The sort of help you'd get from a real-life concierge
Joie de Vivre Hotels
@JDVhotels
Hotel rooms as low as $50 per night, offered every Tuesday
Kimpton Hotels
@Kimpton
Free–stay giveways, Twitter–only savings, and customer assistance
Marriott Hotels
@MarriottIntl
Hotel updates and limited-time discounts of up to 60 percent

TRAVEL ADVICE & EXPERTISE
Airfare Watchdog
@airfarewatchdog
Notification of extraordinary airfare sales
Bing Travel
@fareologist
Airfare and hotel deals and travel news
FareCompare
@rickseaney
Advance notice of steep airfare sales, including "mistake fares"
@flyfrom_ _ _
Plug in your home airport's three-letter code for location-specific fare sales
Gary Leff
@garyleff
Frequent-flier mileage and points advice, "mistake fares," and assistance with creative ways of redeeming miles for free trips
The Global Traveller
@globtrav
Frequent-flier advice and savvy travel tips