Videos
You can search for videos on anything from tying your tie to fly fishing to cooking egg plant lasagna.

Strengths
While youtube.com is sometimes filtered in various institutions, Google Video is usually not
Easily embeddable

Images
Google Images quickly searches for images on any topic

Strengths
Fast & near endless
Filter to block "R" rated materials

Weaknesses
Easy to inadvertently use copywrited images

Scholar
Searchable research articles on millions of topics


Books

Strengths
Search for full text of books

Weaknesses
Difficult to save books offline
Missing pages (this is to circumvent copywrite)
Format hard to work with for some