"They have a free and paid service and their free service gives
5GB 2GB storage, which is what I am using right now. Dropbox is yet
to open up their API (planned) but you can still do some really
nice things with it like creating a virtual machine with virtualbox
and save it on your dropbox; you can open up this "virtual disk"
from any other machine with virtualbox and when you make any
changes to the VM it gets synced and saved, so that you can go to a
third computer to use the virtual machine and the changes will be
there.
"When you first create a virtual machine, it uploads the
"virtual disk" to dropbox, which can take some time depending on
your upload speed but once its created it gets synced with all your
dropbox client computers."