Org - an Emacs mode for notes and project planning http://staff.science.uva.nl/~dominik/Tools/org/
viki[1] has some (highlighting) support for todo lists but it doesn't sort them for you. I also started building some pim functionality on top of it but haven't got it to actually work & to test it so that you could rely on it.
Thomas. [1] http://www.vim.org/scripts/script.php?script_id=861
