Obsessed, to be even more efficient in advice-providing, I suggest that you include SugarSync as an alternative to DropBox which is equally powerful and easy to use, and also free,
but has two very big advantages which make it a winner in the contest:
it offers 5,5Gb+ for free (when DropBox offers only 2,3Gb), and you can choose ANY folders in your hard disk and point them to be synced as you please.
In DropBox, you have to put contents to be shared in a separate specific folder, and this is quite limitating.

Since I was referred to SugarSync, I've chosen it as my first cloud-sync site and left my DropBox account for other stuff.
It works splendidly in Android (/Ermine) and you can sync many devices simultaneously.
I have three in sync (notebook, PC and Edge), and it's the perfect companion for the Edge.