I’m kind of surprised that this software hasn’t been mentioned here yet (that I’ve found, at least). First off, the site:
TextSoap is a program that cleans text. It’s hard to get any more specific than that because there’s so many options. I personally use TextSoap the most when I’m preparing content for publishing online (served as Editor-in-Chief at Inside Mac Games, and publish my own stuff elsewhere). However, it is also incredibly useful in a number of other scenarios, and thanks to the fact that it supports regular expressions and some very powerful custom cleaner abilities the options are pretty wide-open.
I highly recommend the deluxe version of the program: the contextual menus make using the program ridiculously easy.
That said, there’s some issues with TS. One big one is that it sometimes does really weird stuff with RTF encoded text that has different styles in it. Every once in a while I’ll run a cleaner on a bunch of text with one bold word and have it all come out bold. Thankfully the dev is very responsive, so this kind of thing will hopefully be fixed soon.
This is one of those programs that you really have to download and try out. It’s really hard to explain why it’s a cool piece of software, but it’s found a solid place in my workflow.