Few years back I made a presentation for a technology company and needed small icons of computers. Let's say if I needed it today. I can go to icon finder, type in computer and I can choose from various images.
We can filter these images and choose 'Allowed for commercial use (No link required)'. You can now use these images and don't have to provide a link as well. You can also forget about any license infringement. However, I suggest providing a link wherever possible to promote a site which gives you cool stuff for free. To filter by license, look at the drop down menu at the top right corner of the page.
We can also filter images by size and background colour. These options are there on the top just below the search box. Once you click on an image, you can download as PNG. PNG works just like a JPEG or GIF file. Once you download on your system, you can insert it in your presentation.
What do you think about this site? Do you think you will need it in your presentations?