For computer-related stuff where filenames were once severely limited in length, I used to use YYMDD, and more recently YYYYMDD. The month is compressed to one letter by making it base-13 (no zero, though) and using A, B, and C for 10, 11, and 12. Thus, Halloween this year is 1999A31 and U.S. Independence Day is 1999704.
The nice thing is that (at least in the ASCII character set) the letters come after the numbers when electronically sorting, so dates are properly sorted in year order, then month, then day.
As for people-readable, I’ve preferred “1999-August-30” or “1999-Aug-30” so there’s never the possibility of confusing the month with the day. The English-language problems are apparent which, oddly, the short abbreviation form above fixes: if we went with YYYY-M-DD and used base-13, there would never be a day-month mixup.
Oh, and the 99-VIII-30 format is a neat idea (although a little clumsy) until a couple years from now when 01-II-03 could be 2001-February-3 or 2003-February-1.