1. FontAwesome (墨刀內置圖標庫):http://fortawesome.github.io/Font-Awesome/icons/
2. Ionicons(iOS/Android系統圖標):http://ionicons.com/
3. The Noun Project(標誌牌圖標):http://thenounproject.com/
4. Icon Finder (圖標搜索站):https://www.iconfinder.com/
5. Icon Font (阿里圖標庫):http://www.iconfont.cn/
6. Google Material Icons:http://google.github.io/material-design-icons/