there is already a good collection of screencasts at http://learnplone.onenw.org (thanks to Jon and others) and http://zeapartners.org/scl/ (thanks to Paul) and http://www.upfrontsystems.co.za/plonedocs/movies/ (thanks Joris Goudriaan and Roché Compaan)

here are some ideas that i had for Plone screencasts:

groupware features

• publish a calendar from iCal/Sunbird to a Plone site (Calendaring + Marshall)
• create a collaborative workspace (TeamSpace)
• create a discussion board (Ploneboard)
• create a mailing list (listen)
• create a wiki (wicked)
  

web 2.0

• create and subscribe to RSS feeds (basesyndication/fatsyndication)
• display external RSS feeds in a Plone site (feedfeeder)
• create a directory of books in your Plone site (ATAmazon and Amazon API)
• create a directory of links in your Plone site (Tasty Bookmarks or azlinks)

content authoring

• drag-n-drop page layout using  CompositePack (Godefroid's CompositePack screencast) 
• more advanced Kupu features (photo placement/resizing, inserting internal/external links, configuring whitelists/blacklists)
• using external editor to edit files/documents in your Plone site
• automatically converting MSWord/Open Office documents to HTML

searching

• full-text indexing/searching of MSWord/PDF docs (use Kapil's patch to Archetypes.BaseObject.SearchableText method)
• using custom-search for more advanced searches

forms generation

• creating web-to-email forms with PloneFormGen
• creating Archetypes with ATSchemaEditorNG (use SignupSheet as example)

workflow and versioning

• submitting, reviewing and publishing content (walk the user through the process of typical Plone workflow) - Workflow screenshots
• versioning using CMFEditions  (Paul's screencast - Paul - why doesn't this appear in the list of screencasts?)

I'm sure there are others, but those are just a few off the top of my head.
anyone interested in helpful create these screencasts?

there's a good tutorial about how to get started here:
http://wiki.showmedo.com/index.php?title=Requirements_for_Screencasts
Using Camtasia - http://showmedo.com/videos/series?name=ScreencastingInWindows
5 Tips for Making a Screencast - http://blog.showmedo.com/?p=59