GVFS (https://wiki.gnome.org/Projects/gvfs/backends) now provides a package that lets you log in to your Google Drive account and access it from Nautilus, but you have to be on GNOME for it.
This is very cool and I use it from time to time, but it's not actually keeping anything synced afaik (it's equivalent to the web ui, but very nicely integrated in gnome).
And KDE has kio-gdrive for the same thing with Dolphin.