LaTeX resources

This is slightly off-topic, but this is probably the right group to

I'm about to initiate a group of 1st-year graduate students into the
mysteries of LaTeX, and in particular to the mysteries of writing
semantics equations, proof rules, etc., in LaTeX.  

I have my own body of LaTeX2e macros and the source code for my papers
that they can look at, but I'm looking for other resources they could
use.  In particular:

(1) What packages do you find helpful for writing semantics papers?
    Please comment on usability, documentation, etc.

(2) Do you know of any guides to good TeX coding style, particularly
    with respect to the difficulties of typesetting semantics?

If there is sufficient interest, I'll summarize to the list.