Another thing that really helps is short row bust shaping. With short rows, it only adds fullness in that particular area, and the rest can still be more form fitting. Short rows can also be used to accomodate larger hips. It's a whole lot better than an all-over 'big' garment that gives enough room for the areas that need it but like you say makes you look like a whale.
I haven't really looked at this book but a lot of people are raving about Big Girl Knits
, you might want to check it out.