Water, water, everywhere... is there a clean drop to drink? That question would be easy to answer if you had brought along this little number from Katadyn.
There are dozens of water purification options on the market, but I found this to be the most straightforward. The filter is internal to the water bottle, the cost is reasonable, and best of all... it is easy to use (which means I will actually use it).
You can find this unit in most good outdoor / camping stores.