Here are some pictures. Read on for context.
So, if God ever comes down and says "Joseph, you must change your religious beliefs. Pick from the following menu of pre-approved religious doctrines," I now know exactly what my decision would be (yes, I know that the premise of the question pre-necessitates some changes in my theological outlook. Bear with me here). I'd pick Sufism in a heartbeat. I know next-to-nothing about Sufism (other than that it's a mystical branch of Islam that believes that love is God's reflection on the universe. And truth be told, I had to search the Interweb to figure out that last little detail). But their religious practices look like so much fun!
So, a little background. There is a tomb West of Khartoum (in a town called Omderman) for a 19th century Sufi leader named Sheikh Hamed al-Nil. The tomb is in the middle of a large cemetery, and every Friday the local Sufis have a religious ceremony known as the dhikr, where people try to work themselves into an ecstatic frenzy to better commune with God. There's a little opening act with a band, playing for tips (presumably for upkeep of the tomb, but I don't really know). The real meat of the evening is the chanting and dancing, though.
It's really quite impressive. There were probably around 50-100 people participating. Most of them were chanting ("La illaha illallah", which means "There is no god but Allah"), some were playing drums, which evoked a very hypnotic atmosphere. Many people formed processions that marched around inside this circle of onlookers, chanting and shaking staffs in the air and dancing. The most fascinating to watch, though, was by far the people who would throw themselves into ecstatic motion in the middle of the circle. They would spin in circles (the "Whirling Dervishes" of which you might have heard), run around the audience, throw themselves onto the ground, and basically just try to lose themselves in physical action and activity. One man in particular spun himself throughout the entire evening (which was a good 45 minutes, I'd guess -- maybe more). He was going fast, too -- I'd guess a good 1RPS was the slowest he ever went.
It was amazing to watch how involved everyone got. It reminded me in a way of being young, six or so, and going onto playgrounds, jumping off swings, trying to hold onto the merry-go-round as you spun it as fast as you could, hanging up-side-down from the monkeybars, running around in circles trying to make yourself dizzy. That kind of wild abandon, where you're trying to overload your brain through the shear overwhelming sense of activity and adrenaline overload, using disorientation and movement to clear your mind and disconnect yourself from the outside world. So many people were in these amazing, brightly colored Jellabiyas as well, which is an interesting change from the much more conservative and plain clothing that you generally see on the streets. The man who walked around in the particolored robes with the pointy hat, sharing incense with the crowd, was a particularly eye-catching sight.
I don't much go in for religious ceremonies. I've been to a fair number of them in my life (I was raised Quaker, if you didn't know, so even most Christian ceremonies are a novelty to me), and by and large the ones I've enjoyed have been in spite of their format and traditions (because of a well-written sermon, say, or some nice music). So often it feels like any sort of meaning that I might get out of it is needlessly hidden behind these arcane rituals that exist for no real compelling reason, other than "hey, that's the way we've always done it." (By far the least pleasant experience I've had with this is at the Temple of the Tooth, in Sri Lanka, where every evening they have a ceremony to unveil the tooth of the Buddha that they safeguard. We went to see the ceremony once, which consisted of droning, hypnotic music with no variation for at least a half-hour, which is when we decided to leave.) The dhikr was awesome 'cause it was just so joyously unstructured, leaving it up to everyone to participate in the way they chose. I can't imagine I would really get any more sense of meaning or religious value out of it than from any of the other options. But it'd be so much more fun to try!