Speaking of swimwear, and having tried on swimsuits recently (and in the middle of winter--nothing like that experience to remind you that you're not above working out!), I thought I'd give some advice for addressing your problem areas:

1. To hide a tummy, try ruching, shirring, A line tops, and layered ruffles.  I have a ruffled tankini that I love! It hides my belly (my problem area) but still looks cute and fresh.

2. For troubles in the rear (end that is), try full briefs, boy shorts, swim skirts, and/or swim dresses.  A nice new option is high waist bottoms.  Typically they have a retro fit which includes ample rear coverage.  Now, I've read advice that says adding more fabric actually makes the area look bigger and I think that can be true in some cases but I just can't see wearing a string bikini bottom because my butt is big.  It just wouldn't feel comfortable for me!  BUT this was expert advice so I thought I'd throw that caveat in!

3. For a large bust , try V cut (wearing a bandeau or really high neckline will make them look even bigger and give you the forbidden uniboob) or scoop neck. 

4. For a small bust, try a deep V, underwire tops (lifting up what you do have), lightly padded cups, or volume on the bust (i.e. fringe (a big trend lately), floral, ruffles, etc).  Check out this post I did last year on small busted swim options.