FiltersFast.com

Full review
The website sells air and water filters for all kinds of products--from refrigerator, sink, pool & shower to air & HVAC, plus tons more; water test kits; hoses; etc.  Buying in bulk saved me not only money but time since they carry many, many different brands. You can search by type of filter, by brand name, or by size needed. There is also a lot of information regarding various air and water contaminants, the truth about bottled water, and a great user forum where people can ask questions and learn from others on a variety of products, situations, and troubleshooting.  The website was easy to navigate, and prices seem reasonable.  I received email communication promptly after placing my order and again when it shipped, along with the tracking number.  Loved the $1.99 shipping for placing a minimum order of $75.  My order came really quickly, and was packed well.  Unfortunately, the item I ordered was listed as a equivalent to the item I was really looking for--not really the fault of FiltersFast.com, because all websites seems to list the item as a comparable even though it is NOT.  [NOTE:  American Plumber Sediment Filter W5W is not the same as Pentek CWF--the former is a 5 micron filter, the latter is a 10 micron filter.]  I contacted Customer Service and the rep (Katie) was VERY helpful and patient.  She answered all my questions and directed me to various products that might suit my needs.  I wished I could have re-ordered with FiltersFast.com and save myself the restocking fee (and because the rep was so nice to deal with) but I eventually had to place an order with another company.

All in all, I would definitely recommend FiltersFast.com, just make sure you know exactly what you're ordering so you won't have to return anything and get hit with the restocking fee (which I guess is an industry standard).