My husband and I have been thinking about a rain catch system for a while. We live on a mountain and moving water around the property is a big challenge. If we could set up a rain catch system we could capture the water here at the top and then use it during the dry season for pastures or animals on the down slope during the dry season. Given we are located at the top of a huge hill, we wouldn't even need a pump we could just gravity feed it.
I came across this pin from www.familyhandyman.com and I am impressed! We have a bunch of old 50 gallon barrels that we would use instead of the trash cans so the screen system built into the lid would have to be modified. The rest of the system is easy just PVC connections. This system even has the overflow to account for periods of lots of rain. I think I would just funnel it to another holding tank given that here in California we need to capture as much as possible while it lasts because it doesn't last long. You could basically set up the exact same system again at the end of the overflow though and catch double the amount represented here.
I had been picturing a cumbersome system that was a challenge to get the water from but this one here makes it easy to hook a hose to and use rather easily. The Family Handyman article outlines the materials and building procedure really well so if you have been thinking about a system like this as well, I recommend you go check it out.
Another fantastic resource is available at Backyardboss.net. Step-by-step instructions explain why the rain barrel makes sense and exactly what you will need to tackle each step. Everything from building a cinder block step (as opposed to the wood, which I kind of like because it will hold up longer), to installing the spigot and dealing with getting a good seal. The finishing touches will get you ready to start collecting and insure a steady supply of water.