I usually don't use many plugins for Vim. Today, I tried some new:
o vim-calendar: Shows a calendar in Vim. A simple "<Leader>cal"
does the job. Very handy when writing new TODO items.
http://www.vim.org/scripts/script.php?script_id=52
o vim-calc: An interactive calculator that runs in a Vim buffer. No
need to leave Vim. Use Vim commands to edit your formulae, yank
the results, (almost) arbitrary precision, ... Depends on Python,
though. That is, requires gVim on Arch Linux.
http://www.gregsexton.org/portfolio/vimcalc/