Travel booking sites.

Recently I have been travelling a lot and always been looking for good sites to find the best air fare and schedule which suites my needs.
In this field, I would advise folks not to use www.makemytrip.com in case they are booking the tickets from behind a corp net or a firewall. It appears to me that their servers caches a IP-Address to request mapping, possibly in the cookie and doesnt clear it even after you clean up your browser cache or change your browser or machine altogether. So, dont be surprised if you go to this site, ask for Flights from Delhi to Mumbai and you end up seeing results for Cochin to Kolkata. This is because somebody in your corpnet might have used this site to search for flights for these locations and you and your colleague sharing the same IP Address for the external world, would screw up each other queries.
I would suggest, use travelguru.com which doesnt seem to have this problem and by far cleaner than previous site I mentioned. But I found that the air fares on this site were comparably higher than the actual fares one can find on the airline site. This could be because of two reasons:
1) Either the travelguru site takes extra commision from the airline (unlikely),
2) Fares have been dropping since last two months, and hence airlines have updates their sites but travel sites haven't.
I am yet to try other good sites in this business but by far I am not satisfied with the quality they deliver, specially when you are entrusted to pin your credit card number on such sites.