images.google.com.au
Or go to Google home page and click 'images' in top left.

Results from first image search

Look for the gear-like symbol in the top right of the page - click on that to get to Advanced search function.

This is the advanced search page. Scroll down to the bottom, where you see options for selecting images based on their licence conditions.
I selected "free to use share or modify" for this example. This encompasses a range of CC licences, including the basic attribution licence, as well as those with share alike or non-commercial provisions. Visit creativecommons.org.au/licences for full details.

HOW THIS WORKS:
When the images are loaded into the website the image owner will have entered the copyright licence information in the metadata. Google trawls through metadata to get these results. (There are likely to be more openly licensed images on the internet but if they lack the appropriate metadata, Google won't be able to find them.)
In all, this works pretty well. But to be on the safe side, always check the original website from which the image was found. This is explained in following slides.

You will notice that the search results have changed. These images should, technically, all be shared with some sort of open licence.

Screen grab of image detail function on Google image search. Note the options it provides - "Visit page" [go to original website], "View original image" [shows the file that was loaded to the internet] "More info" which leads you to more Google search options.

Always check with the original website. This gives you a chance to double-check the licence conditions, and also gives you an idea of where the image comes from (if you're interested in that sort of thing). You never know what else you'll find on the website!

There are the ducks I want!
From here you can right-click to save the image to your clipboard or desktop or wherever (if permitted to do so... see the next step).

Hover your mouse over the Creative Commons License link and look in the bottom left of the browser screen - that will tell you what sort of licence it's protected by. This one is non-commercial, share alike, which means if I want to use it I can't use it in a profit-making venture, and I also have to release my work under the same licence - non-commercial, share alike.

Keep things simple for yourself by looking for images that just use the Creative Commons Attribution licence.

Make sure you credit the photographer and link to the website where you found the image (not the google search page).

How to search for creative commons images presentation by Ruth Jelley is licensed under a Creative Commons Attribution Non Commercial ShareAlike 3.0 License. http://creativecommons.org/licenses/by-nc-sa/3.0/