Presentation software

Wikipedia has a very general introduction to this field http://en.wikipedia.org/wiki/Presentation_program  

Higher Education Academy Subject Centre websites http://www.heacademy.ac.uk/ourwork/networks/subjectcentres

are sources of subject specific guidance and resources for use with PowerPoint

Multimedia

Advice and support for a variety of media that can be included in PowerPoint presentations is available on the learning technology group website here:  http://www.lancs.ac.uk/celt/celtweb/elearning_good_practice

Support for PowerPoint

Information Systems Services run training courses for PowerPoint and offer desk side tutoring

http://www.lancs.ac.uk/iss/training/staff.htm

TechDis for advice about accessibility and PowerPoint (among other things): http://www.techdis.ac.uk/index.php?p=6_2  

Guidance specifically about effective color contrast, designing for people with partial sight and color deficiencies

http://www.lighthouse.org/accessibility/effective-color-contrast