Anybody set up a system to collect rainwater while camping in the rainy season?

I've never tried it, but it seems like a tarp would work just fine if properly tied/anchored. Have it drain into a bucket or something.

I backback and typically hammock with a tarp. In areas with limited water I will catch the tarp runoff in my wide mouth water containers. It's nice because then I don't have to filter!

How do you set things up?

A 20x20 tarp suspended between 4 trucks channels lots of water when it rains.

On a smaller scale, Hennessy Hammocks make funnels to channel water off their tarps into standard soda bottles.
http://www.hennessyhammock.com/new-products.html#water

I'd filter it anyway...

in the southwest its doable but for the most part it rains mud here. so grabbing rain water for start off drinking is pretty icky.

Just stretch a line between two sturdy objects and clothespin a tarp to it. Having a 2-gallon bucket or something for it to drain into would be handy.

Even in the desert, after it's rained for a few minutes, there's much less dust/sand in the air. You could just strain it through a bandana or coffee filter.

Rainwater is far cleaner than ANY groundwater. I wouldn't worry about contaminants. What you're probably getting from your municipal supply or well is probably far filthier, you just don't know it. Ignorance is bliss, right?

Sue

So, what should the backpacker bring to capture rain water to refill camel backs/similar systems when a body of water is not readily available-but rain water is?

A few months back I set up my hammock as a storm was brewing. I needed to get water, but the rain kept coming down hard. I decided to wait for the rain to abate a bit, but it never really let up. Not to mention that I could see the water that was roiling in the streams was getting muddier as it went on. Decided just to put my collapsible sink and a Nalgene underneath the points where the water was streaming off the tarp. Worked beautifully. No squatting awkwardly by a stream, trying to balance a bottle. In an hour and ten minutes I had collected 6 liters of water. Kept transferring it into a 3L Camelbak, until it was full, then another Nalgene, then the other Nalgene, and then let the sink fill up. Much cleaner then the water I would have gotten from a stream.