I like Haute Look. It's a "daily deals" site run by Nordstroms that closes out designer name stuff. I have particularly good luck scoring my odd-sized normally-very-expensive bras on there for $20, $25 a piece every few months. Most things are returnable too, even though they're closeouts.
coldwatercreek.com they aren't the cheap polyester clothes they were years ago. I like to look at customer reviews and comments about the clothes, and you can avoid a strange fit or find out how sheer some things are too from the reviews.
I went to the store first, and found out what size I wear, and then bought similar items in more colors online. Plus online usually has better sales, than in the store, and the size and color selection is usually better too.
Title Nine http://www.titlenine.com/home.do. And, not just for athletic clothing...I get some dresses and skirts there too (my work does not requre formal business clothing, but does have a basic dress code). I have a hard time finding clothes that fit me well without alteration (tall, slender, narrowish hips, broad shoulders, boobs...), I find the clothes from Title Nine tend to fit me fairly well.
Poshmark! If you aren't picky (since a lot of girls get their stuff at consignment stores) you can find some SUPER deals. I scored 6 pairs of maternity pants, brand new with tags, for under $50. And they are usually open to bartering a little bit as well.
I love ModCloth too, but want to comment that reading the measurements is a MUST!
I'm 5'2'', just out of college, and generally dress very youthful, but I have sent back many a dress to ModCloth because they were so gosh-darned SHORT! And I am not talking "Oh, it was too high above my knee!" but like "Oh, I just got a glimpse of my underwear!"
Now that I've smartened up and know what my "minimum length measurement" is, it's a much better shopping process.