Anyone who intends to use the new LaTeX in any real way is strongly encouraged to get a copy of LaTeX: a Document Preparation System (2nd edition) by Leslie Lamport. The ISBN for this book is 0-201-52983-1.
An additional source of hardcopy information on the new LaTeX is The LaTeX Companion , by Goossens, Mittelbach, and Samarin (ISBN 0-201-54199-8). It has lots of examples and explains the use of several LaTeX packages.
The following PostScript documents may help you learn the new LaTeX. They will not serve as a replacement for Lamport's book. Please use restraint in printing.