To plan your trip: cruisecompete.com.
Best for: Cruises.
Winning features: Choose a cruise and, within a few days, the site’s network of 400-plus travel agencies will search for the lowest price they can offer for it. Most customers receive five to seven quotes via e-mail; these may include perks like cabin upgrades.
Weak spots: Since prices generally aren’t published on the site, you could spend a lot of time looking at cruises that are well beyond your budget. This site works best if you have a sense of the costs of different types of cruises.