Though TeX was originally designed for use with mathematics, many packages exist for use with the sciences as well.
Aside from mathematics, chemistry seems to be the subject for which the most TeX packages have been created. Information on a few such packages have been linked below. There is also a system called ConTeXt, which is based on TeX, that includes a module specifically designed for the drawing of chemical structures and the typesetting of reactions called PPCHTeX. It is theoretically possible to have the same functionality with LaTeX by loading the m-pictex and the m-ch-en packages which are part of ConTeXt, but this is difficult to implement.
chemfig package explains how to draw molecules in LaTeX, as well as how to diagram reaction schemes.pst-labo package provides macros for the drawing of many basic and complex objects which are used in chemistry laboratories. The terminology used for the various objects and apparatuses are French, but a list of the terms used is presented toward the beginning of the guide. Its implementation may require some knowledge of the underlying pstricks package, but a lot of the basic functions are easily understood.m-pictex and m-ch-en packages in LaTeX.There does not seem to be many packages designed with the subject of biology in mind. Those which have been linked to below are related to genetics and graphically showing genealogical relations.
pst-pdgr package provides macros for drawing medical pedigrees according to the recommendations for standardized human pedigree nomenclature using pstricks. An interface for making trees is also provided.pstricks package. Unfortunately, the text of some of the templates are in French. It should not be too difficult, however, to understand the gist of what is being done.There is some overlap between the symbols and operators used in mathematics and physics, so many of macros in the amsmath package will be of use in the context of physics as well. There are, however, a few specific packages related to physics, a few of which have been linked below.
physics package provides macros for use with linear algebra, vector calculus, and Dirac notation.hepparticles package provides macros for typesetting high energy particle names.circ package allows for the creation of circuit diagrams using LaTeX. It also has the functionality to create basic optics diagrams as well, though a more robust package for optics is linked below.pst-optic package allows for the creation of fairly elaborate optics diagrams. The package utilizes the pstricks package, which is loaded automatically when pst-optic is loaded.