These are a few websites I have practised programming on:

https://www.codingame.com/home
https://www.codeeval.com/
https://www.hackerrank.com/
https://www.codewars.com/dashboard

Here are a few more of interest to me:

https://www.reddit.com/r/dailyprogrammer
http://up-for-grabs.net/#/
https://www.topcoder.com/