NoteTab Pro ($19.95 at http://www.notetab.com/ is not (quite) free, but does the job exceedingly well -- with any kind of paren, brace, etc... and I think its free l'il bro, NoteTab Free, does so too. update:WIN only, but as I recall, supports all since 95. YMMV.

Also has quite a library of plugins to support perl and various other languages, html, css, etc... with a tabbed interface to let you work with multiple files open. It's quick and small.

No, I don't work for 'em, but I like the package so much I'm glad I paid for it. FWIW