Until last year when I actually started to focus more on the physiology of sex, I would have answered maybe three. After an exciting year of meeting some wonderful ladies, present company included, I have to say many more. 
While we are born with 'standardized' equipment, many of us have read the sexual experience is 80%+ in the brain. (I do not claim that the following terms are industry-accepted, just used for discussion.)
1. Standard orgasm - whatever the 'normal' is for a guy.
2. Retrograde orgasm - where you feel the effects of orgasm, but due to the clenching of Kegel (PC) muscles, no ejaculate. Can be intense, but also uncomfortable, especially if it has been a while since the last release.
3. Compression orgasm - Instead of using the PC muscles to stop an ejaculation, rather, the lower abdomen is expanded down and out, pressing against the two nerves which reside on the top of the penis to the left and right of the center line. This delays the ejaculation without the PC pressure. Very nice. Requires concentration and an inward focus for a bit.
4. 'short prep' orgasm - The 'Quickie'. When you swant one fast. Doesn't have much of an 'after-life'.
5. 'long prep' orgasm - Take an hour to keep on the edge of cumming, but not going over. After about 10 minutes, it is very nice to switch to a light touch to stay at attention. When you finally decide to release, it is like your essence is draining out. Very, very intense.
6. 'soft' orgasm - where one is not hard, maybe a '2' on a 1-10 scale. Not as intense, but can feel 'comforting' like being enveloped.
Some variations which add more to the above:
A- when with that special someone, making direct eye contact, your faces an inch or so apart, can be transcedental. A feeling of 'losing oneself'.
B- shared breathing - either both breathing in and out at the same time, or one in and one out. With the latter, it is like exchanging energy. A feeling of consuming and being consumed. Wow!
C- If one is receiving a BBBJ or HJ, and your Lover is running her hands from your member outwards down your thighs and then back up again in a circle, at the point of orgasm it can feel like electricity spreading, your member hot, but your legs very cool. Very nice.
Finally, there is the Floragasm. Each lady can bring something unique, and this one is very memorable. It doesn't occur often enough, but is sought out like a fine wine. 
I could go on, but I'll let others jump in.
-- Modified on 1/8/2008 4:03:56 PM
-- Modified on 1/8/2008 10:29:51 PM