New York & Company is one of my new favorite places to shop. While they tend to be quite pricey, they have good sales and a good amount of their shirts can be classified as modest while still being fashionable. This peach shirt is from there and the material is light and cool, but still thick enough around the top and middle to resist being transparent. The only problem is that black shines through (as you can see with the skirt) but as long as you wear white on top you have good coverage.
My skirt is from I.N. Studio and was from my cousin. I haven't seen anything else on their website that would qualify as modest, but as with most clothing companies you can find something wearable every once in a while.