This vim6 plugin will automatically load cscope.out databases into vim when you open a C file. (headers included)
It does a search starting at the directory that the file is in, and checking the parent directories until it find the cscope.out file. The idea being that you can start editing a source file deep in a project dir, and it will find the correct cscope database a couple dirs up.
This version also creates some macros and a menu that can be useful. If you don't like them, you can set g:autocscope_menus to 0 and the menu and macros won't load.
See also its entry at vim.sf.net.