I carried in an Uncle Mike's Belly Band for a While
... the one with the attachable holster, as metioned by another poster above.
Pros:
1) Very versatile. I could wear high or low, strong or weak. I normally wore it right over my solar plexus, weak side in about the same orientation one would have with a shoulder rig. Main reason for that is that I'm about 20-30 lbs overweight, and there is a natural "valley" between my man-boobies and my spare tire.
2) Inexpensive. This was my first holster, and not having any idea how I wanted to carry, and not wanting to blow wads of cash on something I would ditch in a few weeks, I got the holster to tide me over while I researched my options at my leisure.
3) Concealable. As mentioned above, it is very hard to detect. Also, it does not limit my choice of clothing as would an IWB. I can wear a T-shirt untucked, or a tucked-in button down shirt. In the latter case, responding to a situation would sacrifice some buttons, but who cares? I carried at my office for about 6 months this way and nobody ever noticed, even two trusted people who I told that I was carrying.
Cons:
1) Comfort. Do not try to wear this without an undershirt. Especially if your torso is hairy like mine. Even with an undershirt, after 8 hours your chest hairs may be all bent and pulled different ways from moving around. This was never too much of a problem for me - I would just go to a stall in the men's room and take it off for a minute and scratch the hell out of my chest to get things back in place.
2) Accessibilty. In some cases it may be harder to access your gun than an IWB. With an untucked shirt, you have farther to reach for the gun if you reach up under the shirt. With a tucked shirt compared to a tuckable IWB, it's probably about the same because in either case you are tearing at your clothes to get to the gun.
Hope this helps.