Note lectures accessed online with the full website address. Provide the professor's name, the date of the presentation and the title of the lecture or PowerPoint presentation. Note the usage of PowerPoint in brackets and provide the location from which you accessed the PowerPoint slides. For example: "Bluth, G. O. (2003). The Aztec Tomb [PowerPoint Slides]. Retrieved from http://www.poof.com/illusionsnottricks.ppt." Note that this is following the American Psychological Association citation style.
Cite the PowerPoint associated with a professor's lecture as any other lecture but include the notation that your are citing the PowerPoint slides. For example: "Moriarty, James. "Removal of Obstacles." PowerPoint presentation. 21B Baker St., London, England. 12 Dec 1893." This example is in the Chicago Style Guide format.
Credit PowerPoint slides found on a professor's blog or website as you would any other electronic resource. Often presentations can be uploaded apart from a lecture. These require the same author, title, date and location format as any other citation with the added need for a URL and indication that the resources is PowerPoint based. For example: "Dodson, Antoine. "Bed Intruder." Huntsville, Alabama. PowerPoint Slides. http://www.waff.com/story/12883477/woman-wakes-up-to-find-intruder-in-her-bed. 29 July 2010."