There are lot of addicting websites on internet that could waste lot of time specially social media websites like Facebook. Usually if you open Facebook then you go through walls and see video then open any article with good headline after then open another post and it waste lot of time and could take many hours. If you are entrepreneur or have any startup on internet then you need focus and time management to achieve your goal and for it you need to block websites or any addictive gaming app that you could do by few apps that me suggesting below.
Cold turkey is a free app that block website and apps that you can setup easily with their option panel. They have easy time table for blocking website plus its almost impossible to unblock website or app after setup. You can install it on your employees PC or for students lab on your school and it will be hard for them to unblock. You can get cold turkey app from here plus you can donate to them if its useful for you.
Rescue Time is a time management app that tell how much time you spent on social media or any other website and app for free but if you need to block website then you you need buy their package. You can use it if you need to track your time but if you worrying for your privacy and need simple or small app then its better to use Cold Turkey app.
Self Control is a free open source app for Mac OS X that block websites, mail server or anything easily on internet. You could use it as an alternative to Cold Turkey for Mac. Its free and you can even help them for making this app better on Github.
I hope these apps suggestions will help to block distracting websites or any addictive app to save your time and focus easily on your project to achieve your goals.