I'd agree with trying rompers and maxi dresses, especially those made of really light-weight fabrics-- cotton, thin jersey, etc.
Also, you could try some sheer layers to mix it up? A sheer blouse maybe, or a lace overlay tank?
I don't really know a whole lot about warm weather dressing, seeing as I could basically wear a jacket the whole year round, but I think the above might give you a chance to mix it up without making you too hot and sticky. xD