Obvious-Mode is a project mainly written in Vim Script, it's free.
Clearly indicate visually whether Vim is in insert mode
This is a mirror of http://www.vim.org/scripts/script.php?script_id=2212
Clearly indicate visually whether Vim is in insert mode via the StatusLine highlight group.
When you go into insert mode, the status line color changes. When you leave insert mode, the status line color changes back.
Github repo: https://github.com/bsl/obviousmode