Hi Friends,
I am sure you all must have had a discussion on this topic and I do not intend to stretch that further 
I just posted something about classification of Siddhis and my viewes on my blog.
Siddhis
We live in the modern world that is backed by science and technology. Since childhood we all are taught to test or look for some proof about various things in our life. For doing so we apply various ways ranging from experience to laboratory tests. We tend to believe the things that are tested by modern science and tend to reject the things which are not proved or discovered by the science. Indian Yogis possessed many psychic or spiritual powers which are called as Siddhis. In the modern world many people discard the concept of Siddhis because modern science has not proved their existence. Doing so is a sign of narrow mindedness as per my opinion.
You can read the complete post at http://www.bipinjoshi.com/displaythread.aspx?threadid=242&forumid=13