A better option would be SugarSync, although it doesn't have a Linux version (yet - since it has a Mac OSX version, I would imagine/hope they are working on Linux support)...
The downside to Dropbox is it syncs only one folder. SugarSync lets you define multiple folders,
among other things.
It also has lots of mobile options (see above link): iPhone, Windows Mobile, Blackberry. Android
It's free version gives you 2GB, but has a few limitations - only two PCs (but you still get mobile support), and only two versions (yes it supports multiple versions), and the paid versions are reasonably priced - the most expensive is the 250GB plan, for $25/mo or $250/yr.
I haven't tried it yet but I'm planning to do so soon.