So I know there are a number of gardeners / handy-persons on this board, so does anyone have a recommendation on DYI or inexpensive rain barrel systems?
I'm looking to do a quad group under my deck stairs and am looking for any suggestions and/or hints.
Unless gravity will be our friend for once, I'd start with figuring out and getting your hands on the pump you'll need to service the plan(s) in mind... unless you got a lot of coffee (I mean an unhealthy amount) and as defined a muscle tone as Quagmire.

So what's this gonna be for? Suplimental irrigation? We can get something pretty cheap that'll run a hose or two for a couple rotary lawn heads.
The storage system is easy (plastic barrels or I've done a home-made system where I took some plastic garbage pails, 2" PVC, and a caulking gun to link them all up) the collection method can be wide ranging and easy or complicated-er.
In the early 90s we were having some bad droughts here in SoCal, so my family devized this pretty elaborate settup that, long story short, we diassembled about 6-8 years ago because the cost and pain of maintaining the pump was not worth the savings/effort, and it still only would cover about 2/3 total irrigation needs. Ours was a pretty beefy pump though, as our back yard has a good uphill slope to it from the bottom where it starts, and it tied in with our normal backyard irrigation system, requiring at least ~7.5gpm @ 35psi, idealy in the 45-55psi range. Our water source was the washing machine discharge, with septic/eco/friendly detergent in it (yeah, was a real PITA if you discharged a super bleach-rich load from some whites or something into the "tanks"). Since it wasn't ever enough we'd dilute it with fresh water anways to be safe to our plants. If we would collect rain and hold it for when the weather warmed up, we would need to treat it or store it in an underground tank so it wouldn't turn into an algea or mosquito issue before use (and big-underground is the only way to really store a sizable amount of rainwater to do you wany good going into a hot summer). The laundry detergents would nix that need for treatment though, for the whole few days before we'd use it up. Just run it through some filter and dilute it and it was good to go through the pump and to the lawn.
In the end I just look back on our endevour with some shame, all the effort, plumbing and wiring that went into getting it all to work safely and nicely, but that's because I think we just went too big, particularly when it got down to the pump requirement and being a small residential with a big slope in the backyard. Would of probabley worked out a lot better with some sears/honda electric sump pump and a couple rotary heads on the end of a garden hose (and in the end been a lot less wasted effort/work/$ and been a lot better money/effort saver as it was intended).