You may not have realized it, but Eclipse (and derivatives-- Aptana, Titanium, etc) can be run as a "portable" application. Meaning, you can just copy the entire Eclipse directory to another computer or, say, a USB drive, and it will run exactly the same, with all of your settings in tact.
This means it is a perfect friend for Dropbox. I place my Eclipse IDEs in folders under Dropbox, and make sure my Workspace is pointed to a folder within Dropbox, and presto-- my projects, settings, etc, are on all of my computers and ready to go.
And any changes I made to my source code, preferences, layout, etc, are automatically spread to my other computers.
Now, this does require that your Dropbox folder is at the same path location on all of your computers. But, luckily, Dropbox lets us specify exactly what path to use. So, for example, you could just make sure that your Dropbox folder is always at C:\dropbox.