What to mount on

Cork bark is very popular. It is attractive, light weight, easy to cut and will not rot when wet. It is generally available. A little expensive maybe, but worth it, and you won't be using all that much. For those like me who think big, you can get a 300 pound bale and never need to ever buy it again.
Driftwood can be very good as long as it is a hard wood. Redwood is available to us on the west coast. The thing to watch out for is that it is salty. I let mine sit outside through a rainy season. That gets enough salt out so that I can use it for mounting. A couple of washings with the hose will not do the job. If you can't wait a few months for the rainy season, put the wood where the lawn sprinklers will hit it.
Hardwood branches are great. Any kind of fruit wood works well. Grape is always available here and it can have some interesting shapes. Let it sit outside until the bark comes off and it has seasoned.
Tree fern fiber plaques work. They come cut in convenient sizes. 4"x6" is about a buck. They hold up well to watering and are easy for the orchid to attach.
Wood slotted baskets are used commonly for Vanda and Ascocenda but they are great for mounting other orchids. I have several Phalaenopsis in baskets on their side. Any of the large rooted orchids will do well in a basket. Great for those who want to water often.