Giardia Water Filters - Tips and recommendations on avoiding giardia and using water filters while backpacking, trekking and hiking. - http://giardiaclub.com
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
TheBackPacker.com - Reviews of water filters, as submitted by the users. - http://www.thebackpacker.com/gear/water_filters/
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