Working abroad is basically the same as working at home. I use Skype and Mail all the same way. But working on long term projects means sending and keeping track of a lot of files.
I use a simple Project Collaboration Tool, accessible online, that allows me and the people involved to keep track of everything we share, including different versions of the same files. Users can download, comment, annotate and so on. A useful tool vastly adopted by my clients.

For those interested, check out activeCollab. A Basecamp-like to say it short. I found some decisive advantages over Basecamp though : no monthly fee once purchased, storage on my own server, fully customizable, and superfast with a proper hosting service.