Most of the information in these other sites addresses preparation of a scientific poster session. Posters in the social sciences and humanities may not contain all the elements illustrated here and may be produced on presentation boards instead of full scale posters. But the principles and guidelines remain the same across all disciplines.
Online Tutorial from University of Leicester
This short tutorial covers the basic elements of preparing a poster session. Written for a UK audience the tutorial references European paper sizes but the design and layout information applies regardless.
Presentations & Poster Sessions - LibGuide prepared by Sarah Walkowiak at Brandeis University. This site includes a number of interactive tools that demonstrate spacing and other visual elements of poster sessions. Includes links to printing companies that prepare full-size posters from your digital file.
Designing Communications for a Poster Fair is a very clear, easy to read and understand guide developed by Pennsylvania State University for the McNairs Scholar Program. It is linked here with the permission of David Strong. This website also links to other similar sites. (Note: as of October 13, 2008 some of the links on this site are dead). A PDF version of this guide is available below.
Designing Conference Posters by Colin Purrington at Swarthmore College is also an excellent (and humorous) overall guide. This guide includes sample templates, for use in PowerPoint, and a bibliography of useful articles.
There are numerous other guides available, both online and in published in journals, detailing proper preparation of a presentation poster. A Google search for "poster session preparation" or "poster session guidelines" will return more results than you would care to read.