Dropbox is really handy in that it automatically syncs your changes made locally to the cloud and then carries those changes into the local copies of anyone you've shared the files with. You can share single files, directories or entire sets of nested directories (great for projects). It keeps archives of changed files and deleted files, for recovery and rolling back to previous versions. I use it when collaborating and it really eases the tech pains by integrating with the operating system on the mac or pc. I recommend it. There's more room if you want to pay but the free version offers 2GB with 3 more gig available by referring new users. Which for me has happened naturally as I've shared documents with people I work with.