Being somewhat of a frequent traveler for work, here's my two cents:
- Corporate travel web sites, used for weekday business travel, oft times give nice rates for leisure travel, such as when renting a car, use the corporate agreement, to get the negoiated rate. Conversely, corporate travel web sites are absoutely terrible for business travel. It's an irony that generates a lot of discussion among coworkers.
- The best way to compare prices is to use Expedia, Orbitz, and Travelocity, all at the same time. There's nothing stopping you from having three browser windows all opened at the same time, and use all three to look for the best deal on hotels/airfare/cars. Usually, one of the three sites will have a real good deal on something, and it will be obvious. Beware Expedia, with hotel rooms, though. They buy rooms in blocks, and you get charged for the room right away, not when you check in, even if you don;t check in.
- Travel Bidding sites (priceline.com, etc.) are very useful if you have knowledge of the hotels in the area, specifically what star rating (2,3,4) they fall into. BiddingforTravel.com and betterbidding.com have forums where people post what their bid results were, i.e., you get to see what bids were accepted or rejected. BiddingforTravel has a developed a bad rep, of supressing or modifying information, though. Still, interesting to see what others say there.
- johnnyjet.com has a huge amount of speciality web sites listed, you have to dig down through all the gunk to get to them, though.
- There a new website named kayak.com that is getting a lot of buzz, it's supposed to be competition for Orbitz and Travelocity, was started by former employees from both places.