TopTal
Some time ago I found a letter in my mail box inviting me to join www.toptal.com. A brief look told me that this was a kind of freelance portal, similar to oDesk.com and rentacoder.com (now freelancer.com) I worked on earlier. The difference is that TopTal makes you pass the screening process before letting you in.
After a brief Skype conversation with their recruiter, I was given a link to codility coding tasks. I do not consider freelance seriously any longer and didn't expect anything tough from "just another freelancer.com", so I decided to work on it on Friday evening after drinking couple of beers :). In fact I was wrong and that's where I failed.
I do not remember all of those tasks, but one of them looked interesting. I made a screenshot and decided to solve it later, when I'm able to concentrate :)