Well, since we have a new forum and I have played with this some, here is my take on a simple DIY water heater.
Sure you have seen pictures and some how too's but everyone has diff needs so "roll" your own!
I used this on my above ground pool and it worked great. I let it freeze one year (yep it does that here too) so I have moved on to real panels now that I get on GL for about nothing. (another thread on this)
I used just 1 roll (100') I believe and got 95F+ out of it in direct sunlight, showing about a 5-10F rise from the cooler pool.
I used the included pool pump (intex) and garden hose sucking from the filter onto the roof of a shed (8ft rise) and running into the above ground pool. Just used 1/2 drip line (cheap).
Here is a link also to a little more on it;
http://rimstar.org/renewnrg/diy_pex_solar_hot_water_thermal_dn.htm