Dropbox works great on linux, but at some point the gnome 3 nautilus dropbox shell extension stopped working for me. The shell extension provides little icons over all the files in your dropbox folder indicating their status, and (more importantly in my opinion) the dropbox context menu which lets you link to files, especially those in your Public folder. Here is how you can manually install the very latest version of dropbox-nautilus for your version of Ubuntu.
Add the dropbox linus repository
Add the dropbox public key
Get an updated repository list
Get the latest source code for nautilus-dropbox
Install of the of the necessary dependencies
Install some packages necessary for compiling software in general
Change directory into the directory created for your source code, mine was labelled "dropbox-1.4.0"
The README and INSTALL files are good to review at this point, they go over the basics and details of installation this package.
Following the README, we'll first configure the package.
Next we'll compile it with make.
And finally we'll install.
At this point we have installed the latest version of nautilus-dropbox from source. We'll have to stop all running instances of nautilus and then reopen it to see our changes.
That's it! Just run nautilus, or open your file browser as you normally would and you should have the latest version of dropbox's shell extension up and running.