You might be interested in some of these blog posts. These are most of my still-working links to stock tanks used for gardening:
http://www.penick.net/digging/?p=1610
http://www.succulentsandmore.com/201...or-bamboo.html
http://www.penick.net/digging/?p=7566
http://caylawral.blogspot.co.uk/2010...to-finish.html
http://thinkingoutsidetheboxwood.blo...in-garden.html
http://thinkingoutsidetheboxwood.blo...ie-garden.html
http://twomenandalittlefarm.blogspot...vegetable.html
And a few links to my area of interest. Australian practitioners of permaculture have long used "wicking beds" for water efficiency, which can be as simple as a pond liner recessed in the ground with a wood or corrugated metal "raised bed" frame. Another take on sub-irrigation. I have seen a few "wicking worm beds" using stock tanks that are fully self-contained, but most use corrugated metal without a base:
http://www.resilience.org/stories/20...e-wicking-beds
http://www.milkwood.net/2010/05/11/h...a_wicking_bed/
http://permaculturewest.org.au/resou...cking-beds.pdf - PDF with diagram.
http://www.maireid.com/wickingbeds.html
Same principle as my sub-irrigated stock tanks. Since I have not modified my tanks, I could easily sell them for 75%+ of what I originally paid in, say, 5 years should the need arise. I have seen 10 year old leaky 300 gallon tanks sell immediately on Craigslist for $200, when you could buy a brand new one for $250. Go figure.