The internet is a vast and confusing place. Here are some sites that I've used and been impressed with. Send in you own recommendations or feel free to slate mine. Let's try and get a top ten list of sites which are really good.
Try Laterooms for hotel rooms (Worldwide) up to a year in advance. I've used it twice and you get a huge discount off the room rate. You can read reviews of the place which hopefully haven't been written by the management.
Confused.com will almost certainly find you a cheaper insurance quote for your house or car. You have to type in endless tedious details, but it's probably worth it. I renewed my house insurance for little more than half what I was paying before. If you manage to get a good deal, please be so kind as to send me a cheque for 10% of whatever you save.
ps I've now got my car insurance with them also.
Take a look on tripadvisor to see whether your 'quiet and romantic' hotel is actually above a nightclub or has a nice view of an oil refinery. There is obviously some debate as to the validity of the comments but I've found it spot on.
cdwow! have sold me cheap cds and dvds which actually arrived.
Flickr is a great place to find photos of just about anywhere. Print them out and pass them off as being from your last Round The World trip.
Google Maps is astounding. Zoom right in on your own house and...wait a minute- that's not my car in the driveway and who is that with Mrs C?
Bonusprint do online photo printing. I've used them half a dozen times and they are great. Top quality even for large blow-ups and very fast. Make up a nice calender and give it to Granny for Xmas (your Granny, not mine)
None of the above sites are paying me a penny for these recommendations, but I can assure you that they would get far better reviews if they did.