1. When I write (on paper) I always write the month in words and the year in full. So 9 August 2010 or 9 Aug 2010. No uncertainty there.
2. When I name files or folders, it's always YYYY-MM-DD.
MM/DD/YYYY is a most miserable convention.
http://www.cl.cam.ac.uk/~mgk25/iso-time.html
One point which makes me love this one is that it's "easily sortable and comparable", which is great when you have tons of files in a folder.
it would only be (relatively) better if i were turning 42.