Ddldbl.vim is a project mainly written in Vim Script, it's free.
Delete Duplicate Lines and Delete Blank Lines.
This is a mirror of http://www.vim.org/scripts/script.php?script_id=484
This is just a normal ol plugin; NOT ftplugin (there really should be a plugin option in the type field when adding a new script... hint hint :) )
This is a quick/simple implimtation to delete duplicate lines (:DDL) and delete blank lines (:DBL)
Both commands can take a range and DEFAULT TO THE ENTIRE FILE. Both of these commands delete lines so be carefull!
:DBL (delete blank lines) is little more than a command front end to a :g command. :DDL (delete duplicate lines) opens folds, starts at th top of the range and goes down. For each duplicate line found it is :delete End result is you can select a portion of a file and quickily and easily delete blank lines and or delete duplicate lines.