I was watching another one of Kurt Schwehr’s Emacs videos and came across something I didn’t know (or at least something I’d forgotten). You can center text on the line with 【Meta+o Meta+s】. By default it will center the line the point is on but you can center N lines by specifying a prefix. Thus to center the next 3 lines you would type 【Meta+3 Meta+o Meta+s】.
That’s handy for those times when you’re producing a text file and want to center text for headings or whatever. The centering respects the fill column so it’s always accurate.