There are a lot of different breathing exercises, they are generally called pranayam.
You can search Google with this term to find more.
As for the "best", it all depends on the purpose you have in mind. All of them are beneficial, but there will be those that are more specific to a desired effect. Search for pranayam yourself to find out more.
Here is a page I found for you with several pranayam:
US $132.50
There are a lot of different breathing exercises, they are generally called pranayam.
You can search Google with this term to find more.
As for the "best", it all depends on the purpose you have in mind. All of them are beneficial, but there will be those that are more specific to a desired effect. Search for pranayam yourself to find out more.
Here is a page I found for you with several pranayam:
http://www.wikihow.com/Do-Pranayam