Procraster is described as 'Procrastination management app' and is an app in the Office & Productivity category. There are four alternatives to Procraster for a variety of platforms, including Google Chrome, Mac, Windows, Linux and Chrome OS. The best alternative is LeechBlock, which is both free and Open Source. Other great apps like Procraster are Cold Turkey (Freemium), StayFocusd (Free) and Time Companion (Free, Open Source).
LeechBlock is a simple free productivity tool designed to block those time-wasting sites that can suck the life out of your working day. All you need to do is specify which sites to block and when to block them.