I've heard, though I've not formally met any wiccans in reality, that it is sometimes pronounced Bless-Ed Be. Sort of pronounced where the ed is spoken seperately, but I was never sure if people saying it that way were saying it wrong or not as it sounds odd, but so does old English or phrases like thee. Other faiths use similar sayings like blessed day, have a blessed day, blessed day to you, etc... I'd just pronounce it the way it's spelled when in doubt. The only other sayings I know which are highly commercialized is merry meet, merry part, and merry meet again which in my mind means it was good meeting you and I hope we meet again in the future. Google is a nice if sometimes untrustworthy tool, so just google Wiccan phrases.