It depends on the brands you want to buy. If you have a local Discount Shoe Warehouse (DSW) retailer, they are very low in price, and have all the major brand names.
Lots of websites online are having regular sales on new nike running shoes. Two of the best deals can be found at sportsdirect.com and also at milletsports.co.uk
You could find cheap but supportive running shoes online at ebay.com. Ebay will offer many running shoes that are quality shoes and will be able to help you out.
you can go into your local footlocker, sporting goods store, or big 5. They carry the Vomero running shoes. You can try them on, speak to a sales associate who specializes in shoes, specifically running shoes.
You can visit running shoes guru and run and become, you can find a reviews about neutral cushioned running shoes. They will also suggest good quality neutral cushioned running shoes.
http://www.newtonrunning.com/ Gives you information on newton running shoes. The sales and prices and everything you need to know about the shoes you plan to buy.
Go to foot locker and go to the clearance section to find running shoes on sale. They want to sell them and off their inventory. You will find some deals there for running shoes of all kinds of sizes.
Since your getting running shoes for a marathon, I suggest you go to the major sporting stores and/or shoe stores. The sales people will help you out, fit you, and find the perfect shoes for you.
For great Nike women's running shoe sales you can look on websites like roadrunnersports.com where they have a great outlet section for women's running shoes. For in store sales I would try places like foot locker, because they will almost always have a good sale section.
SimplyRun offers wide range of running shoes, running clothing, running sport watch & heart rate monitors with best prices, best quality and fast delivery.
Amazon is always a good place to start as cheap stuff is on it and lots of high quality running shoes. Sports direct is also cool and it is like a sports version of amazon.
Look on Amazon.com since they often have sales on shoes. I got some very nice running shoes for around 30 dollars one time. You can also do a gooogle search for shoes and it will give you a wealth of information.
There is almost always a sale going on in some store on mens trail running shoes. Put on your shopping cap and get ready! Websites such as REI, Finish Line, Amazon.com, all offer great deals and sales. The closer it is to a holiday, the more sales you can find either online or in stores.