Albert Einstein once said: "Everything should be made as simple as possible, but not simpler." That's exactly what TripIt does.
All TripIt does is aggregate all data that you get from confirmation emails when booking flights, hotels, rental cars, ... . Adds in bits of information scraped from the likes of wikipedia, the weather channel, google maps, ... . It doesn't require a genius to come up with this, parsing some standard generated emails is a piece of cake. Adding in extra info may require a bit more effort, but still isn't rocket science. Nothing all that brilliant at first sight, but here's the catch.
It's dead easy to use, it's fantastically thought through and cleverly crafted to minimize your effort. The lazy web at it's best.
Really, all you do is forward those nasty gibberish confirmation emails. Tripit will figure it out for you. It doesn't require a lengthy, time consuming, sign up procedure. Since you sent them an email, they know your name and your email address. That's enough personal information for one day isn't it?
Once you forwarded your first mail you get a nice return mail (caught by my company spamfilter, but they are aware this happens often, unfortunately). That return email contains a link so you can quickly go check out your travel plan, at that point you'll be prompted by a "real" sign up, which has a nice skip button. So you can easily use it without having to register. Ever!
Further in that return mail is also a username (your email address) and a password, for future log-on purposes.
Finally, to add in some 2.0-ness, you can share and discuss your travel plans with friends (or colleagues) and figure out who out of your network is close to you. I still need to get some friends hooked up on this, so I can start checking this thing out :)
Conclusion. Awesome, it simply does what it needs to do, without making it complicated, time consuming. And since 90% of the population uses the same top airlines, travel agents, car rentals and hotel chains, it's able to parse everything most people will ever need (you can still manually add/change if you really have to). I know the year is still long, but this is already a huge contestant for my personal "tool of the year" award!
Also check out the demo videos. It really is that simple.