Bedding is something that every horse person who stables horses has to deal with every day.  It changes the nature of compost piles and the rate of decompostion. Differing types of bedding has different acidity for putting compost or bedding and manure straight back onto fields.   It also has different absorbancy rates and can be more or less comfortable for the horse.

Pine Shavings:

The most widely used bedding in the United States and here in Minnesota is pine shavings or sawdust.  It is very comfortable for the horse and is easy to deal with when picking out stalls.  Its problems are that it is dusty, it doesn't compost as fast some of the other bedding and it is pretty acidic which is not good for soils with high pH.

Newspaper:

This newer option got a lot of people excited when it first came out.   It composts really well, is soft for the horse,  and it is economical.  Not to mention that it is recycling post-consumer paper products.  But, it has its problems that usually out weigh the benefits for most potential users.  It is a pain to pick out becuase when it gets wet it just turns into a soggy mess.  People are worried about horses injesting the print ink and it tends to fly around the barn and yard in windy wheather because it is so light.

Straw:

An old stand by.  It doesn't have the problems that pine shavings do, but it is hard to pick out and not as absorbant as some of the other bedding.  The positives are that it composts and decomposes very well, is comfortable for the horse, and it is economical.

Pellets:

Dust free and absorbent, but expensive and not comfortable for the horse.

Wood Chips:

Also dust free, but not as absorbent and also not comfortable for the horse.

Hemp:

I personally think hemp is the way to go.  It is comfortable for the horse.  It is super absorbant.  It composts and decomposes really well.  It is useing a plant that doesn't leach nutrients out of the soil it is planted in and doesn't require much in the way of herbicides or pesticides.  It is completely dust free.  It is easy to deal with to pick out stalls.   Its only problem is that hemp cannot be legally grown in the United States, so this bedding must be shipped from Canada, which raises its price.  It is economical if you can buy it in bulk and store large amounts of it on the farm.  But many farms do not have the luxury of having enough space to keep a years worth of bedding.