- Advent of Code is a daily challenge during September, with time-based leaderboards. Usually only 2-3 that wind up taking more than an hour, and the early problems should be approachable to almost anyone.
- ICFP Contest is an annual weekend event typically in July/August. Expect to be wokring on the problem space full time, all weekend.
- Synacor Challenge by the guy behind Advent of Code, I haven’t done this yet.