L2T extracts excerpts of Lisp (Scheme), C, or Perl code from files and incorporates them, for instance, into TeX files. It can also conveniently pretty-print or convert parenthetic Sexpressions into trees, drawings, Greek denotations, etc.
LyX is a document processor that encourages an approach to writing based on the structure of your documents, not their appearance. It is intended for people people who write and want their writing to look great without tinkering with formatting details, font attributes, or page boundaries. On screen, it looks like any word processor, but it uses the TeX engine for printed output and producing richly cross-referenced PDFs. It is stable and fully featured.