Tmarks is a project mainly written in Vim Script, it's free.
Browse, place, & delete marks
This is a mirror of http://www.vim.org/scripts/script.php?script_id=2594
Also available via git: http://github.com/tomtom/tmarks_vim
This plugin provides commands to browse and to manipulate (place & delete) marks.
:TMarks Browse all marks.
:{range}TMarksPlace Place the next available a-z mark at the specified line.
:{range}TMarksDelete Delete all a-z marks in range.
:TMarksDeleteAll Delete all a-z marks in the current buffer.
In conjunction with vimscript #2584, this plugin is similar to vimscript #152.
You might want to try wokmarks (vimscript #2522), which I personally use now.