Simple vim script for a single centered text column.

focus.vim

" Name:    focus.vim
" Author:  Alan MacDougall <smoke@alanmacdougall.com>
" License: Public Domain
"
" Focus on a single column of text, showing it in a distraction-free format.
" Save this as ~/.vim/scripts/focus.vim (or whatever you please), and invoke
" it with :source <filename>. Of course, you could certainly hook that up to a
" :command, or a macro, or a Vimscript function...

" collapse current splits and divide screen in three
only
vsplit
vsplit
"
" hide the tildes for nonexistent lines
hi! NonText guifg=bg guibg=bg
" hide the vertical split borders
hi! VertSplit guifg=bg guibg=bg

set laststatus=0 " hide status bar
set noruler " hide ruler [I prefer to leave this out]
enew " edit new blank file, i.e. clear screen
set nocul " hide cursor line highlight, if present
2wincmd l " move to right-hand split
enew
set nocul
wincmd h " move to center split; happy typing!

Screenshot:

Just open a new gvim/MacVim window before doing this, since there's no provision for reversing the effect!

there is also the VimRoom plugin

Yeah, this little script is very specific to my own setup and needs. I'm really fortunate that MacVim fullscreens at greater than 80 * 3 + 2 columns on my 27" iMac, for instance, meaning my centered column is wide enough for an 80-column text view. To universalize it would involve enough work to where VimRoom is probably a better solution. :)