If you are specifically looking for maxi dresses for buying, I would suggest that you go through this collection first. You will find all the exclusive maxi dresses collection in this online store. Check it yourself for more.
Maxi dresses are in season right now so you probably won't find them on sale but you can find them better priced. If you have a papaya store or body shop near you they have them there normally never more expensive than $25. If not they both have online stores. Places like tjmaxx, Marshall's, or Ross has them at low prices and are sometimes really nice brands. Brands like hollister and American eagle have started carrying maxi dresses and if your lucky you might find some on sale there too. Good luck!
On shopping mall you will find maxi dresses on sale.
I live on east coast, so im not sure if this will change depending on ocation, because some stores dont go country wide. Anyways, i get soooooooo many dresses, especially maxi dresses at TJ Maxx. I love it there! Especially now that its spring/summer, there will be a lot out.