First off, we Buddhists do not worship any diety, not even the Buddha. We revere the Buddha for his teachings, but he is not a god.
As to your question, it is the worlds fourth largest religion in the world with somewhere between 400- 500 Million follower (about 6% of the world's population).
Alot.
There is no god(s) in Buddhism. As a consequence there are no worshippers. Buddhists frequently turn their attention to the example of Buddha as an inspiration, but as he is only a man there is no anticipation of divine intervention or blessing.
approximately 2,700,000 people follow Taoism
6 million
It is said that there are 360 million adherents of Buddhism in the world today.
Buddhism evolved by that buddha shared his knowledge around Asia and the followers decided to become Buddhism. Today in 2012 there are not many people that believe in Buddha.
Today, Buddhism is probably least evident in many of the Muslim nations. Countries like Saudi Arabia, outlaw any religion other than Islam.
There are many groups of Buddhism in Japan today. The main ones are the Pure Land Buddhism (Jodo shu and Jodo Shinshu) and Nichiren Buddhism. There is also Zen (Soto and Rinzai are the main ones), Tendai and Shingon. Many new religions also are based on Buddhism.
Lots, try googling "National devil worshippers registrar"
Because Buddhism is taught in many different ways; through books, teacher-student relationship as well as the direct experience of mind it is probably taught in many different nations of the world in all kinds of conditions.
India
India