If you are going to be out you will definatly need a water filter!
I chose the MSR Sweet Water Microfilter, found it on eBay for just $63.99 shipped.  I like the lever pump action style better than the pump or grip pump filters.


The MSR SweetWater Microfilter gives you a fast, dependable way to filter your water, and only adds 11 ounces to your backpack.  Simple brushing restores a clogged filter, and the pump lets you know when the filter needs replacing. Fold the handle down and slip the 7.5 x 2in SweetWater Microfilter into the included stuff sack. Also include 80-micron stainless steel prefilter.  Eliminates over 99.9999% of all waterborne bacteria and 99.9% of common protozoan parasites, such as giardia and cryptosporidium for Fresh Tasting Water: Activated carbon core helps eliminate taste and odors. Easy to Use: Unique lever-action pump handle has a 4-to-1 mechanical advantage, pumps water on both up and down strokes for a fast 1.25-liters-per-minute flow rate.  Lightweight: Weighing just 11 oz., it`s one of the lightest filters on the market. Compact: Handle folds flat when not in use for easy packing and storage. Includes: SweetWater microfilter, 80-micron stainless-steel prefilter, (2) color-coded silicone hoses, foam float, water bottle adapter, cleaning brush, and stuff sack.