I sell a Mathematica Application, Presentations, that is designed to aid in writing custom graphics, tables, dynamic displays, and literate notebooks in general. It sells for $50 through my web site.
A few years ago someone on MathGroup had a similar question and I wrote a KeyEquations sub-package for Presentations that gives much more flexibility in writing, editing, recalling and referencing key equations. You can specifically format equations and their labels. The labels may be sequentially numbered (and updated) or textually labeled.
I am attaching a PDF copy of the tutorial notebook for this. (I will send a copy to any reader of MathGroup who requests it.)
From: Nicholas Chisholm [mailto:firstname.lastname@example.org]
I've been trying to use Mathematica to keep organized notes of my work because it's easy to typeset equations. Is there any way to format how equations are labeled in notebooks? For example, using the "DisplayFormulaNumbered" puts numbers on the right of equations, but is there anyway I can format these numbers? Say I want an equation called (1a) and (1b) or something instead of (1) and (2). I've been messing around with trying to edit the stylesheet to no avail.