Clip arts are images such as illustrations, borders, backgrounds that created by hand or by computer software. The term originated through the practice of physically cutting images from pre-existing printed works for use in other publishing projects.
Finding a clip art from the web is easy, but not all of them are reusable, they are copyrighted. This page has a list of websites that offer public domain clip arts free for any personal or commercial use.
Open Clip Art Library
OpenClipArt
http://openclipart.org/
Total images: 35000+
Searchable: Yes
Categorized: Yes
RSS Feed list: Yes
Image Format: PNG, SVG
License: Public Domain
WPClipart
High-quality artwork and photos optimized for use with word processors and inkjet printers.
http://www.wpclipart.com/
Total images: 37000+
Searchable: Yes
Categorized: Yes
RSS Feed list: No
Image Format: PNG, JPEG, WebP, SVG
License: Public Domain
Clker.com
The online royalty free public domain clip art – vector clip art online, royalty free, public domain
http://www.clker.com/
Total images: 32000+
Searchable: Yes
Categorized: Yes
RSS Feed list: No
Image Format: PNG, SVG, ODG
License: Public Domain
Public Domain Clip Art
PDClipart.org – Public Domain Clip Art, Images, Pictures, Photographs, Graphics.
http://www.pdclipart.org/
Total images: ± 20000
Searchable: Yes
Categorized: Yes
RSS Feed list: No
Image Format: PNG
License: Public Domain
Public DomainPhotos
8,000 free cliparts for personal and commercial use
http://www.public-domain-photos.com/free-cliparts/
Total images: ± 8000
Searchable: Yes
Categorized: Yes
RSS Feed list: No
Image Format: PNG
License: Public Domain
Reusable Art
Free downloadable public domain images rescued from old print materials
Total images: 2000+
Searchable: Yes
Categorized: Yes
RSS Feed list: No
Image Format: JPEG
License: Public Domain
Old Book Illustrations
Old Book Illustrations – pictures scanned from old books
Total images: ± 1000
Searchable: Yes
Categorized: Yes
RSS Feed list: Yes
Image Format: JPEG, SVG, EPS
License: Public Domain