<C-G>c in insert mode to toggle a temporary software caps lock, or
gC in normal mode to toggle a slightly more permanent one.
If you don't have a preferred installation method, I recommend installing pathogen.vim, and then simply copy and paste:
cd ~/.vim/bundle git clone git://github.com/tpope/vim-capslock.git vim -u NONE -c "helptags vim-capslock/doc" -c q
Once help tags have been generated, you can view the manual with
See the contribution guidelines for pathogen.vim.
Copyright (c) Tim Pope. Distributed under the same terms as Vim itself.