The best ones I know are http://freebitco.in/?r=779433 and http://freedoge.co.in/?r=10440. If you are (very) lucky you can get even 0.4 BTC in one shot.
Wow this sounds great, 0.4 btc really?
Probably there will be a winner every year or so
I don't know. I've got the values from line 1, 2 and 3, but no luck for better values yet. I don't know how often the others happen. I'll let you know if I'll get that :p