Centering text/layers in PS 7

I'm trying to make a graphic that's actually going to be printed on a program, but this would be useful knowledge in general, I think.

I'm trying to center text. I don't mean center-align; I know how to do that. I mean, is there a way, an option somewhere, to make Photoshop center a layer -- say, a line of text -- either horizontally or vertically (or both) within the space of the graphic? I'm pretty good at eyeballing it but for something this important I'd like to be precise, if I can.

Thanks!