Target! The clothing there is made by a ligitiment designer and the prices aren't high at all. There is a bunch of cute stuff there, where as in t.j. maxx and marshall they get the clothes the stores turn away so it's harder to find something appealing there. Also look at Charlotte Russe. They have very affordable clothes. They also have really nice stuff. Goodluck!
Old Navy has cute maternity clothes but they can get pricey...if you don't mind spending a few more minutes going thru the clearance racks then you can find awesome deals.
Ross has lots and lots of maternity clothes and I get a lot of mine there shirts that are under seven dollars and jeans/capris under 15. And most of them are name brand too which makes it really neat.
Another place is off ebay. I get some off there. Make sure to know what size you are in different brands...if not measure yourself and if you like something then ask the seller what the measurements of the garment is. I forgot to do that and got a pair of capris that were too big in the leg area and a shirt that was a medium but it was so stretchy and slinky that it looked more like a bigger large.
Good Luck and hope you find some!!