Places I've checked:
Wal-Mart: Surprisingly good selection. Good for sporty options
Target: A bit more fashion-forward, but flimsy, IMO. Lots of separates.
Lane Bryant: Expensive!!! Well-made, lots of separates. Up to date styles, not many options if you have a long torso.
Catherine's: Fairly expensive, large grandma selection, but a few winners. Good quality.
Fashion Bug: Cheaper and the "youngest" of the bunch. Not great quality, but if you get a new suit every year it's not a problem. Lots of choices.