One thing that caught my eye over the summer was Coir, which is a fancy name for cocoanut fiber. I found some moulded pots made of coir last year that I loved, but they were pricey and I didn't want to spend an arm and a leg on the number I would need this year (DOZENS).
I found bricks of Coir at Pinetree Garden seed company for about $3/brick. Each brick expands to about 2 gallons of medium when water is added. I bought 3 bricks.
I also bought a bag of boiled rice hulls for aboug $3. These add volume and air to the mix. Yes, plant roots need air.
You add the rice hulls about 1 part to every 2 parts of Coir. >>
....and was surprised when they were sprouting in two days!!
All in all, I'm really happy with the mix.