I put this wort chiller together in September '08.  The coils are 3/8" flexible copper tubing, and the little rails are #4 copper grounding wire (found in the electrical department at Home Depot). Perhaps a tad over-engineered, but it does just what it should: that is, stands on its own.

When I first coiled the tubing, it didn't really want to stand up straight.  I didn't understand how it would stay put in my brew kettle.  Also, the whole thing was really springy...  gave you the feeling that it would get banged up, misshapen, and generally behave differently from year to year.  I grabbed a few feet of that grounding wire and soldered it on.

Making it myself, I was able to fit it to the size of my brew kettle.  It's a tall-ish 7-gallon job that I got with an outdoor cooker (turkey cooker, whatever).  The wort chiller is about 8 inches in diameter, and fits inside the kettle with 3 or so inches to spare all around.

One other note: the hose is long enough that it reaches the water supply and drain without moving the kettle.  Highly recommended.

When I used it yesterday, I was able to bring 6-1/2 gallons of wort from 210° to 80° in under 10 minutes.  (Mileage may vary: it is winter in Vermont, and my water is around 40° from the tap.)