Dropbox is a free file storage system that allows me to synchronise several gigabytes of files across several devices.  It allows me to access key files anywhere at any time on any device.  It allows me to work on files in one place and pick up right where I left off in a different place on a different machine.

Evernote is a cloud based note taking application which is available on a variety of desktop and mobile platforms as well.  It has a great feature set and the ease of synchronisation makes it invaluable.  Run on a freemium model, this software is simply to good to pass up.  If you don't use Evernote you really should give it a try!