Ask.com
(Click on Settings in the upper-right corner to set Content filtering.)

Bing
(Click on Preferences in the upper-right corner to set SafeSearch.)

DuckDuckGo
(Emphasizes privacy. Click on More and choose Settings in the lower-left corner to set Safe Search.)

Google
(Click on the  Options icon in the upper-right corner and choose Search Settings to set  SafeSearch filtering options.)

Internet Public Library 2

IxQuick
(Emphasizes privacy. Click on Settings to set Web/picture Family Filter options.)

MetaCrawler
(Click on Preferences to set Search Filter options.)

Yahoo!
(Click on More and select Preferences  to edit SafeSearch options.)