Its called hourglass, its what I have too.
www.debenhams.com/webapp/wcs/stores/servlet/prod_10001_10001_54510+201027050_-1?breadcrumb=Home%7EWo men%7EDresses
www.debenhams.com/webapp/wcs/stores/servlet/prod_10001_10001_54510+200933610_-1?breadcrumb=Home%7EWo men%7EDresses
www.wallis.co.uk/webapp/wcs/stores/servlet/ProductDisplay?beginIndex=0&viewAllFlag=&catalogId=20551& storeId=12557&categoryId=183995&parentcategoryrn=140428&productId=1654226&langId=-1
www.wallis.co.uk/webapp/wcs/stores/servlet/ProductDisplay?beginIndex=0&viewAllFlag=true&catalogId=20 551&storeId=12557&categoryId=145409&parentcategoryrn=140428&productId=1772319&langId=-1
www.wallis.co.uk/webapp/wcs/stores/servlet/ProductDisplay?beginIndex=0&viewAllFlag=true&catalogId=20 551&storeId=12557&categoryId=145409&parentcategoryrn=140428&productId=1716578&langId=-1
Basically anything that has some tretch in it so if the material isnt stretchy that it has an elastic panel so it allows room for boobs and flatters the waist. Needs to be a v neck usually. I have got a couple of bandau (strapless) dresses that work really well, have had to invest on a strapless bra (I'm a ff cup so not very simple) and gt one from debenhams which is great. Looks OK with the straps on too.
The above re just a few ideas as i dont know about your sze or the occasion.