When you say pine mulch, I am assuming you mean mulch consisting of pine needles, not mulch made from the chipping of pine tree waste. In those areas where pine is the dominate tree, such as Paradise Pines, the residents are required to rake up pine needles and in most cases, take them to the dump. My grandsons made spending money performing this task. What does the Butte County dump do with all the pine needles? It is a lot closer to you than Texas. Al

I'm so curious about this. I've gone to HD, to Armstrong, to several independent nurseries looking for "pine bark fines" also known as "pathway bark" for blueberry potting mix.
Most of the time the people who work there tell me that its not available because its toxic and will kill my plants. What's the full story there? And why would it be a key ingredient in the mix if it's toxic? I thought perhaps the idea was to use pine mulch because its more acidic, It sounds like there is a legitimate toxicity issue -- is it perhaps that the needles are toxic and the bark is not?
Calistoga can you shed light on this? Can anyone?

Neither mulch made from pine bark or pine needles is toxic to plants. Wood chips used as a mulch as they are consumed by microbes in the soil will tend to make the first inch of soil more acidic, but as your plant roots are deeper than that, in most cases, it will make no difference. Al

There is a bunch of neat stuff here, including screened vineyard waste, which sounds like a possible ...

http://www.sonomacompost.com/product.shtml

(No affiliation, just wishing I was as close to agricultural options.)

A bit on a rice hull potting soil here:

http://sift.ncat.org/blog2.php/starting-seeds-making-potting-mix

You can always contact a local tree removal service and ask them to dump their next clients ground pine tree in your driveway.
Somebody dumped a ground up pine in the empty lot next door,and I hauled as much as I needed. Darned if some plants went a deep green off of it. The only "problem" is that it breaks down very fast..and I guess that's why you are looking for it?