Crackmes.de, a site for testing reversing skills. Crackmes range from "Very Easy" to "Very Hard" for many operating systems.
Archive contains a 2011 release from Malware Ninja...
"Well after the disappointing take down of Crackmes.de I took it upon myself to mirror the crackmes (thanks for the inspiration @darelgrif) as well as the solutions that were on that site."
Please find the following linked zip that contains almost 1000 crackmes for all levels. Please enjoy and mirror/spread.