When I used to have more time (i.e., when I was a grad student and
without kids), I used to
spend some of it writing (La)TeX macros. Here is avm.sty, a style for AVMs (for HPSG,
LFG, or any other kind of feature structure) and documentation for it
in pdf or ps.
The version here now is 1.02. It differs from the more widely
distributed version 1.00 by (i) interacting okay with the Mainz
array package, whereas the earlier version doesn't, and
(ii) adding a command to make it easy to put sorts (types) at the top of AVMs
and updating the documentation for LaTeX2e.
For drawing phrase structure trees, I use a preprocessor and style file
by Avery Andrews.
Avery has recently rewritten the trees processor in Python. You can find his
current version here.
For the older version, here's the C source as a tar
file, the style file, and some out of date documentation. The version
here is actually a slight adaptation by me that adds some new options
(dot, dash, and none), and the ability to run
as a filter. To use this system, one also needs Emma Pease's tree-dvips.
The macros I use for glossing are one of a number of files called
gloss.sty.
For formatting examples, and other miscellaneous stuff, you can also get my
adaptation of Emma Pease's lingmacros.sty,
cm-lingmacros.sty.
Links to some other LaTeX stuff for linguists can be found at: ling-tex mailing list webpage (Norway), A Guide to LaTeX for Linguists (Essex) [recommended], Alexis Dimitriadis (UPenn), or Ralf Vogel.
http://nlp.stanford.edu/~manning/tex/