Get Your Message Across: Proven Methods for Effective Business Presentations
Graziadio School of Business and Management at Pepperdine University
Tips on providing information, gathering information, and persuading someone to make a decision or take an action.
http://gbr.pepperdine.edu/993/present.html

Presenters University
InFocus Corporation
Numerous free, informative articles ("Courses") and PowerPoint tutorials on content, delivery, and the use of visual aids in presentations. Free downloadable PowerPoint templates for use in designing presentations.
http://www.presentersuniversity.com

Designing Effective Oral Presentations
Rice University OWL
This tutorial examines the similarities between writing and speaking and offers tips on choosing a delivery style, using visual aids, enhancing audience comprehension, speaking to a multicultural audience, and more.
http://www.ruf.rice.edu/~riceowl/oralpres.html