1. Bx Slider Widget for Yii 2
https://github.com/yii2mod/yii2-bx-slider
2. Star Rating Widget for Yii 2
https://github.com/yii2mod/yii2-star-rating
3. jQuery countdown widget for Yii2
https://github.com/russ666/yii2-countdown
4. Sweet Alert Widget for Yii 2
https://github.com/yii2mod/yii2-sweet-alert
5. Yii 2 Tree (jsTree)
https://github.com/arogachev/yii2-tree
6. Infinite AJAX scrolling for Yii2
https://github.com/kop/yii2-scroll-pager
7. Yii2 Toastr Notification
https://github.com/odai-alali/yii2-toastr
8. Yii 2 widget for jQuery Timepicker Addon
https://github.com/janisto/yii2-timepicker
9. DropzoneJs Extention for Yii2
https://github.com/perminder-klair/yii2-dropzone
10. Yii2 extension for Mobile-Detect library
https://github.com/alexandernst/yii2-device-detect
11. Yii 2 imagine extension
https://github.com/yiisoft/yii2-imagine
12. Google Maps API library for Yii2
https://github.com/2amigos/yii2-google-maps-library
13. Bootstrap DatePicker Widget for Yii2
https://github.com/2amigos/yii2-date-picker-widget
14. QrCodes for Yii2
https://github.com/2amigos/yii2-qrcode-helper
15. Integration of materializecss into Yii2
https://github.com/MacGyer/yii2-materializecss
16. SB Admin Theme for Yii2
https://github.com/p2made/yii2-sb-admin-theme
17. Yii2 extension to generate auto number
https://github.com/mdmsoft/yii2-autonumber
18. LinkPager widgets for Yii Framework 2.0
https://github.com/phpyii/yii2-widget-linkpager
19. Asset Bundle for Yii2 with Socicon
https://github.com/rmrevin/yii2-socicon