Epinions: Water Filters and Purifiers  
   Consumer-generated reviews, buying tips and advice, ratings, price information, and searchable in a variety of ways from price to product type.
   http://www.epinions.com/otdr_Camping_And_Hiking-Water_Treatment

MSN eShop: Water Filters and Purifiers  
   A shopping site which also mixes in consumer information, including decision tips, product types available, and features to consider.
   http://eshop.msn.com/marketplace.asp?catId=260&pmpType=1&pcId=2242

TheBackPacker.com  
   Reviews of water filters, as submitted by the users.
   http://www.thebackpacker.com/gear/water_filters/

Outside Online - 2002 Buyer's Guide: Water Filters  
   Outside Magazine's guide to water filters and portable hydration systems, including general information plus reviews, descriptions, and photos of the gear tested by their experts.
   http://outside.away.com/outside/buyersguide2002/water_filters/index.adp

Giardia Water Filters  
   Tips and recommendations on avoiding giardia and using water filters while backpacking, trekking and hiking.
   http://giardiaclub.com