To get the matchit.vim plugin working in Debian Squeeze which allows "%" to hope between HTML tags, C preprocessor conditionals, and all sorts of others, you also need to enable filetype plugins (echo "filetype plugin on" >>~/.vimrc or something similar if your vimrc is complicated), then then copy the macro file into your ".vim" plugin directory, (mkdir -p ~/.vim/plugins ; cp /usr/share/vim/addons/plugin/matchit.vim ~/.vim/plugin/matchit.vim).

Something I was vaguely aware vim did, but had never bothered sorting on this account till today. Now my "5" key (e.g. Shift+5) will become as abused during editing as the TAB key is when typing shell commands in the vague hope it will "do the right thing" when my brain is unsure what to type next.