To support the lid, this is perforated septic field drain pipe cut into 4 inch lengths. 10 feet at Lowe's (enough for 6 boxes) is $3.83. The factory perforated pipe should provide unrestricted flow of water in the reservoir and into the wicking chambers. Pipe is HDPE and considered 'good' plastic.

The lid upside down with the drain pipe attached with plastic ties. Holes were cut in the lid for two of the pipes to provide a wicking chamber. The holes were cut to fit the smaller diameter of the corrugated pipe. The larger diameter then fit under the lid for good support.

16 inch fill tube ($2.07) also from Lowe's found in the sink plumbing area. I don't remember the recycle code but it was considered safe and NOT PVC. Note bathtub stopper to keep the skeeters out. Also a wine cork impaled with a bamboo stick to float in the fill tube and show the water level.

Container ready to be filled and planted. Note the extra holes drilled in the lid for ventilation.

Part of last year's crop in late June. Two tomato plants and one banana pepper per container. Plants are supported with weaving between the steel poles on either side of containers. Poles measure over 10 feet to the top from the ground. For prospective, I'm 5' 11. The tops in the photo are at least a foot above my head. By mid-September plants exceeded the top weaves that had been tied with a stepladder. Containers were not self-watering but that will change this year. Containers 1 and 2 are 26 gallon. #3 is a 18 gallon Sterlite. All were filled with a soilless potting mix. I noticed no difference in the growth or production in all three. Huge crop of tomatoes starting riping in late June and finally ceased production with the first frost in mid-November.

Cost: First Box
18 Gallon Sterlite container from Walmart $3.97
10 foot section of septic drain pipe from Lowe's $3.83 -and this is enough to make 6 boxes)
3' x 50' black plastic mulch (Walmart) $3.63 - enough for many more
16 inch undersink drain pipe (Lowe's) $2.08
Assortment of nylon ties (Dollar Tree) $1.00
-enough for many boxes
Drain stopper (Walmart) $.77
Wine cork and bamboo stick (optional) You are on your own....
Total $15.28

Next Five boxes (each):
18 gallon container $3.97
Undersink drain pipe $2.08
Bathtub drain stopper $.77
Total each $6.82

Now if I can get a self-watering system similar to what emgarderner posted, I can take some vacation this year:
http://forums2.gardenweb.com/forums/load/contain/msg0602015726891.html