Productivity Software (nerdy, sorry)

These are the free things I use all the time, and find myself constantly recommending to friends. They all offer iPhone components that sync to the provided information, so I can enter (and have access to) information wherever I am...

TRAVELING
Tripit: You sign up for free, and then forward all your reservation emails for flights, hotels, etc., to plans@tripit.com. The site parses the information in the emails, and posts your plans online. You can have Tripit friends, who can see your trip plans (though not in enough detail currently), and you can post your trips to Facebook (or not, if you'd prefer). The iPhone app really makes this site useful, with its quick ability to retrieve everything from confirmation numbers to airport maps to weather reports.

NOTES
Evernote: Basic sign-up is free, and is a full application for the Mac, Windows and iPhone. All sync through the Evernote servers, so everything is up to date wherever you go. Evernote allows syncing of text, websites, and (if you upgrade to the paid option) files of all types. This is a very full-featured application, but in its most basic sense it gives you access to all the little snippets of information you come across in daily life, wherever you are.

EVERYTHING
Dropbox: This is the one ring to rule them all. Dropbox is a free service (for 2GB; you can pay for more storage) that creates a folder on your computer that you drop whatever your want into. Whatever you drop in is synchronized (extremely quickly) to the Dropbox server, and then to any other computers you have installed the software on. You can then access the information from the Dropbox website, or from any synchronized computer. You can also share folders with other users, so that all parties can update the information in the same folder. The iPhone app allows you to look at whatever's on your Dropbox (assuming the iPhone can read the file) wherever you are. And you can star items on the app so it keeps them accessible even if you're offline. Do yourself a favor: go to the website and set yourself up. Now.