One of the great things about running Linux on the desktop is that there's a standard for how to customize applications. A well-behaved Linux app will put a config file in your home directory which stores your preferences.
For example, the IM client pidgin does this, as well as tried and true apps like vim and the bash shell.
The downside of putting a lot of time into customizing an app is that, when you work on any other computer, you lose your customizations, or you end up duplicating the effort. Maybe you copy your config file over from the other computer. That's brilliant, but sooner or later you'll probably change one and forget the other.
mkdir ~/Dropbox/shared_configs cp .vimrc vimrc_backup mv ~/.vimrc ~/Dropbox/shared_configs ln -s ~/Dropbox/shared_configs/.vimrc
Now, your .vimrc file is in Dropbox, and your local machine just holds a link to it.
To use the same .vimrc on any other machine, just replace the local version with the version in Dropbox:
mv .vimrc vimrc_backup ln -s ~/Dropbox/shared_configs/.vimrc