It may be difficult, but busty types should avoid strapless numbers during the day. You only want to wear strapless clothing when you are going out in the evening and want your cleavage to be on display (which can have a devastatingly sexy effect --- if it's done right).
Strapless shirts and dresses give little to no support in the bust area and have minimal coverage --- meaning your cleavage will be front and center. Because of the amount of skin you are showing, this is a definite no-no for the office or everyday outfits.
Do it up in a classy way for nighttime. Make sure you aren't showing too much skin. Invest in a fabulous strapless bra and make sure it doesn't peek over the top of your shirt or dress. Wearing a great jacket when you are going strapless is the best way to show a little skin and cleavage and still maintain a classy, ladylike appearance.