Don't forget Compiz Fusion, which was eventually merged into Compiz, but that's the one I remember being the hot one. I thought it funny at the time cause KDE could do all the same things too. But I agree with the parent comment, this isn't "little known" if you were using Linux in the mid to late 2000's you were possibly so mesmerized learning the damn thing you looked up ways to make it look and behave in cool ways.