It depends on the airline. A number of carriers have outlets available in Y, either throughout or in a portion of the cabin. SeatGuru has details on power at seats for many airlines.

As for "other" outlets, I have seen them around on various planes, though there have been discussion about the power coming out of them, and some indications that they aren't necessarily 110V/60Hz. That may be a problem if you plug in to them. I'm not sure if it is true or not, but it is scary enough to me that I wouldn't risk it.

Oh, and from the title of the thread I really thought that this was going to be a thread about how to hook a laptop up to the overhead IFE screens to give a presentation using PowerPoint