Linux Cross Reference (http://lxr.sourceforge.net)
A cross-reference and browser that is designed for the Linux kernel, but works with any large software project.
Indent (http://www.gnu.org)
The indent command indents C++ programs.
Vim (Text editor with built-in indenting) (http://www.vim.org)
A text editor similar to the standard Unix vi editor, but with lots of programming related commands including a very smart indenter. This editor works on both Unix type systems and Microsoft Windows.