Not much to say here, I accidentally ordered way too much Spanish Moss online and need to get rid of a lot of it. If you want some, post here.
Spanish Moss (Tillandsia usneoides) is a subtropical bromeliad, closely related to the air plants you see in the store. It's not a real moss, nor a fungus, nor a plant parasite, but an epiphyte that collects water and nutrients from the air and the tree bark. It's supposed to be hardy outdoors down to zone 7, so if you live in an area that experiences hard freezes once in a while, it should survive.
I've had some growing in my yard that I brought back from Louisiana in December 2010, and it handled the dry California summer just fine, even flowering and setting seed. It got water from the sprinklers and nightly fog though, so keep in mind that if you live in a dry-summer climate, it will need to be watered a few times a week (for this reason it can't become invasive in places like California).
I'm not sure about growing it indoors or using it as a CP top dressing, but I think it's been done. It prefers oak and cypress trees in its native habitat, however in my yard it's growing happily on some kind of South American tree (can't find the name right now). It does best when growing in filtered sunlight.
I just unpacked it all to let it breathe, but I'll pack it back up again and ship it out in a padded 8.5" x 11" envelope.