I've used a free itinerary service called TripIt for my last few big trips. It's not perfect, but it's the best thing I've found so far (Dopplr is another itinerary site, but it lacks many of TripIt's features).

When you travel, it's prudent to keep certain reservation information on hand; like your flight times, flight numbers, confirmation code, hotel address, check-in time, hotel confirmation code, etc. Plus restaurant reservations, meeting times and locations (for business) or information about various tours, museum hours, etc. (for pleasure). If you're traveling to multiple cities over the course of a week or two this can be a lot of information to keep up with.

TripIt automates all this reservation-tracking. Once you sign up with your email address, all you have to do is forward the confirmation emails you get from airlines, hotels, car rentals, and restaurants to plans@tripit.com. TripIt then automatically organizes it all into an itinerary that you can either view online from any computer, or that you can print out and carry with you.

I've never had an airline or car rental not automatically work. All the major hotel chains sync up nicely, although there are smaller hotels whose emails are not in a format readable by TripIt. So those you can enter by hand. OpenTable reservations also work when forwarded.

Entering information by hand is quick and easy (basic name/date/time/location sort of form). It's also easy to get driving directions added for your trip (for the most part, just point-and-click the start and end addresses from the activities already in your itinerary).

There's a browser add-on "trip clipper" I think they call it that allows you to just "clip" info directly from websites and save it to your trip. This is useful especially when you just want info about a handful of things to do at your destination. Just "clip" the museum hours, tour booking phone numbers, zoo events, whatever, so you can print it all out and refer to them while on your trip so you can decide which you want to pursue that day.

Now while TripIt does save a lot of writing or typing, it's not perfect. For one, I don't like how it always shows everything on its site in its "expanded" layout starting from the first item. A lot of scrolling is necessary once you're a few days into your trip, and as far as I can tell it's unavoidable. Highly irritating.

It also uses a lot of pages. On one hand, when I print out the itinerary this does leave room so I can add hand-written notes by each item. On the other hand, it would be convenient to have everything on one page so I could just glance down the page to find the bit of information that I need, rather than flipping through multiple pages to find that tidbit.

A nice feature is that you can "share" your itineraries with people with varying permissions. They can either just view what you've entered, or view and enter additional items themselves. For example, I typically let my mother view whatever I've got in there, so if there's an emergency she'll know not only what city I'm in, but also the hotel phone number, etc. This is less important now that mobile phones are ubiquitous, but they do sometimes run out of batteries or go out of range on a trip. If you travel with friends, you can all clip activities that might be of interest so the planning needn't be done by just one person.

TripIt recently added more "social networking" type of stuff. I think they track your cumulative travel statistics (miles traveled, days on the road, etc.) and you can show them on various websites. I haven't paid any attention to that yet, but I do put various summary things like that on my Facebook page, so I can foresee adding that myself in the future.

Bottom Line: Give TripIt a try the next time you go on a trip with multiple hotels or flights, let it help you keep track of all those confirmation numbers and other info.