My default stop for searching for airfares is at Expedia. Oftentimes, where available, I would book directly with the airlines website itself. For accommodations, I would go to Hostelbookers or Hostelworld for booking hostels, and either Agoda or Booking.com for mostly everything else, though recently, AirBnB seems to be coming on strong.
Recently, I found a rebate website called ShopBack. Basically, you do your online shopping via direct referals from the website and you get cash rebates! The rebates is a small percentage but they have hundreds of merchant site partnerships, so they do accumulate if you do alot of online shopping, and needless to say, you can find travel sales and promotions with ShopBack too! And guess what? The sites that I used are represented!
Not only that, they may do specific partnership with the merchants that provide extra benefits (extra rebates etc), eg. you can find the very best of Expedia promo codes there and you can also use Booking.com discount codes and save. A lot of my friends use Hotels.com, so you can find Hotels.com discount codes now too. Just browse their list of merchants and you'll definitely find something you do use. I mean, ebay, taobao, lazada etc are all there too!!
You can see how ShopBack works in this video if you are still not sure :
Like I say, year-end and Christmas is coming and shopping is fully underway! Strangely, I do not see a Christmas specific promo but you can instead book your travels now at their Boxing Day sales. And if you do think this is useful and want to sign up and try, you can use my referal link here so that I can get some referal benefits ($5). You'll also get $5 for a new signup. Check it out!