I recently saw mention of a program, AvPainter, that looks like it would be extremely useful. Too bad it's Windows-only, at least at the moment--and by "Windows-only" in this case we mean "XP SP 3 or Vista", so if you use Windows 7 you'll need the version that lets you run XP on a virtual machine. (If anyone's found a way to make it run under Mono, please let me know!)
It started out in life, as you might guess from the name, as a way to let you create clothing by painting directly on the avatar figure in 3D, rather than having to figure out how the shapes you intend have to be distorted to go on the flat texture so that when they're wrapped around the avatar shape they look the way you intend. (The computer graphics term for it is "UV mapping"; think of it as if you're Mercator trying to come up with a way to draw a map of the spherical earth on a rectangular piece of paper.)
That's all well and good, and I'm sure that clothiers find it a highly useful program, but why do I mention it here? Because the current version supports painting sculpted prims, and hence should be extremely useful for making tops for use with prim breasts, especially if they could be positioned on the avatar shape so one could easily deal with the places where they join.
I'd be very interested in hearing of peoples' experiences with AvPainter.