Microsoft Word:
Textual Guide from WebAIM
http://webaim.org/techniques/word/
Video Tutorials
https://www.youtube.com/watch?v=fMqID2-km-w
Microsoft Excel:
Video Tutorials
https://www.youtube.com/watch?v=NcWK_nzYXd4
http://www.screencast.com/t/FhKbkcNHSiw (with captions)
Microsoft Powerpoint:
Textual Guide from WebAIM
http://webaim.org/techniques/powerpoint/
Video Tutorials
https://www.youtube.com/watch?v=oe-S1CKEA14
http://www.screencast.com/t/jCQKKDcDn (with captions)
(Linked video tutorials were made by Marlene McIntosh, Off-Campus Program Officer of Cambrain College of Applied Arts and Technology)
Help pages from Adobe on creating accessible PDFs
https://helpx.adobe.com/acrobat/using/creating-accessible-pdfs.html
https://helpx.adobe.com/acrobat/using/create-verify-pdf-accessibity.html
WebAIM's tutorial on PDF, Adobe and Acrobat accessibility
http://webaim.org/techniques/acrobat/
Creating Accessible Flash Content
Creating Accessible Sites in Flash
MAGpie (Media Access Generator)