For inexpensive but effective water filtration, the folks at Emergency Essentials has the Katadyn Hiker water filter on sale for $49.99, generally about $10 off regular price. http://beprepared.com/product.asp_Q_pn_E_WP%20F150_A_name_E_KATADYN%AE+Hiker%99+Water+Filter. This isn't the Hiker *Pro* filter, which provides identical filtration but includes quick connect fittings for the input and outgo hoses, which can be useful but will cost you another $25 if you buy the Pro version. The Hiker is a solid performer, outdone only by the Katadyn Guide imo for output of clean fresh water, good for approx 200 gallons per filter cartridge. I've used a Hiker Pro for 4 seasons of backcountry hikes and camping in the PNW, including filtering for groups including Scouts. I get tired of pumping but there's no disputing, the Hiker / Hiker Pro works like a charm and out-purifies (by volume) my older MSR filter pump.

My hiking backup (always at least two methods of getting clean water) are Katadyn Micropur water purification tablets, which I've used periodically on hikes just to use them up. For emergency preparedness I rotate some Micropur tablets into my bag and have an MSR filter in my bag just in case - I'm committed to keeping a store of water for my family, and we'll drink Scotch before I drink potentially chemical or waste contaminated filtered water. $50 for the Hiker gets me thinking it might be cheap enough to buy as a BOB backup. I was given a SteriPen for a birthday gift last year and have done no more than to test clean a bottle of water, then put it away in an earthquake kit - it works just fine, but the weight savings of 7 oz over the Hiker Pro just doesn't make relying on batteries for everyday filtering worth it to me, but ymmv.