This is going to sound really stupid but today I am thankful for my dropbox. I have files all over the place and I work on them on different computers (PC and Mac), or my iPhone, iPad and other places. If I'm away from home without anything (rarely happens!) I can still access my stuff online and do with it whatever I want.
I am really lazy and it's so nice to have my files synced everywhere. I don't have to try to find a cable, zip drive or SD card. Sometimes I'll find an image or a program I want to install on a different computer and I just stash it in my dropbox. When I'm done, I delete it or move it to its permant home to save space on the dropbox.
I'm also cheap so I just have the free version and I'm always monitoring how much space is available. I seem to be running about about a third capacity most of the time.
This really makes my life a little easier and, for that, I'm very thankful today!