Although probably not well-known, <a href="http:&#x2F;&#x2F;crackmes.de&#x2F;" rel="nofollow">http:&#x2F;&#x2F;crackmes.de&#x2F;</a> is a site I&#x27;ve been using to create &#x2F; upload and also work on challenges for various RE applications for about 10 years now.  I&#x27;d definitely recommend it to newcomers wanting to learn more about RE in general.