If you are curious as to how many times you’ve clicked your 20Ds shutter, use a hex editor and simply check out the numbers located at 95D and 95E in a RAW file.
Not sure if this also works in other Canon RAW files for 30D or 400D etc.
The number you get will be in Hex, so you’ll have to convert it to Decimal. e.g “19 F9 = 6650”, which happens to be what mine were as of tonight.
UPDATE: As it turns out, the above method is a load of bollox and means nothing. Thanks whoeveryouwere on flickr who posted the hint. Go suck a lemon!