No luck with ASCCC or any of the repositories? Using Google Advanced Search is a last ditch way to find resources by license type. Here are directions on how to use Google Advanced Search to find materials with open licenses.

On the Google Advanced Search page, scroll to the bottom and look for the “usage rights” field.
Change the “usage rights” field to “free to use share or modify” or “free to use, share or modify, even commercially” depending on what type of license you want.
Use the other fields to plug in keywords and to narrow your results.
Hit the “Advanced Search” button
The results page should show only Creative Commons resources. Make sure to verify exact license type and terms of use.

You can also watch the following video for a demonstration of a Google Advanced Search:

Here are a few more Google search tips:

To find specific types of websites such as .gov or .edu type in the search box Site:.gov or Site:.edu.
To eliminate specific websites or words you can use a minus symbol before the word. For example, if you want to search for something but do not want Wikipedia to show up in the results simply type in the search box -Wikipedia.
Use quotations around a phrase to search for results containing that exact phrase. For example search for “climate change” will return less, but more relevant results than searching for the phrase without quotation marks.
To find a specific format of resource (such as a Microsoft Word document so that you can modify the resource), type the file type - .doc or .pdf - into the search box.

Additional Tips:

Bing Search Tips

Yahoo Search Tips

Attributions:

Introduction to OER by Rachel Arteaga and Suzanne Wakim. This work is licensed under a Creative Commons Attribution 4.0 International License

The video, "Searching Google for OER" by D'Arcy Hutchings is licensed under a Creative Commons Attribution 4.0 International License