A lot of times I like to run Vim in a single window with many buffers. A nice way to stay focused is to go full-screen and then run the vtreexplorer plugin on the root of my source tree. A simple entry in my vimrc, and I can toggle it on as needed:
map <F12>
:VSTreeExplore <CR>
VSTreeExplorer is available at: http://vim.sourceforge.net/scripts/script.php?script_id=184
Here's the obligatory screenshot.