Do you find traditional suicide bombing to be an unexciting and unimaginative way of ending your life to further your cause? Suicide bomb with style, choose Martyr Mortar technology. Our cannons are real circus cannons, modified for maximum human distance. Put on
your explosive vest, load in, and you'll
soon be flying over cities instead of taking the bus.

For [Doc]http://www.physicsc.../vectors/u3l2a.html Physics classroom. You'll need to read 5 pages to get to the equations I used. [Worldgineer, Oct 27 2004]

[bz] "maximum survivable" would be misleading. Maximum survivable while remaining aware enough to push your vest's explode button, but not survivable long after that.

[lint] Don't push your vest's explode button, and hope for a conveniently placed pile of hay.

(running some basic calculations as a follow up to [bris]'s question)
A bit of internet research tells me that terminal velocity for a person in cannonball formation is about 200mph (can be between 160 and 320 in standing-up-straight formation). Assuming a 45 degree declination angle and no air friction (a large simplification, but then so is using terminal velocity as the maximum muzzle velocity), we get:
vx = 200 * .707 = 141.4 mph
viy = 200 * .707 = 141.4 mph
time in air = 2 * viy / g = 2 * 141.4 mph / 32.2 ft/s/s
tia = 2 * 207.4 ft/s / 32.2 ft/s/s = 12.88 seconds
x = vx * tia = 12.88 s * 207.4 ft/s
x = 2671.3 feet = .506 miles

So, you can have the cannon as far as around 1/2 mile away from your target.

[World] just wondered if you could quickly explain some of your maths - I'm not a mathematician but I love understanding these things. I got the velocity and gravity bits, but was wondering why time in air jumped from 2*141.4/g to 2*207.4/g?

Units, my friend.
141.4 miles/hour = 207.4 feet/second
(how I converted, for your reference):
141.4 miles/hour * 5280 feet/mile * 1/3600 hours/second = 207.4 feet/second

Why this needed to be done is because I know the acceleration of gravity in feet/s/s, not in mile/h/s. I'll link to a nice descriptive page of projectile physics that I grabbed my equations from (I should look these things up in my physics book, but the Internet is much easier).

It was Stonewall Jackson's favorite subject (until he was hit by a projectile, that is). And if it's good enough for a guy who prays while sucking on a lemon, it's good enough for me.