I've been re-using Powerpoint slides quite a bit lately because, though I don't think its as clean, often leading to sub-optimal presentations.
I didn't think this applied to anything else, until yesterday when I re-sent an email I'd sent a month ago to someone who'd requested an explanation of something I knew I'd explained before.
Given how much of management these days is communication, its a good way to think about all the email you send and documents you create: is it potentially re-usable? is it likely to be useful in such a scenario? can be it be re-structured so that it is re-usable? can you store/catalog/index it in a way that you'll remember to re-use it?