Hi Friends!
If you want to have your own website with programming exercises, puzzles and challenges — for your friends, classmates or students — here is something for you, making it pretty easy!
I started my own meek site called CodeAbbey more than 10 years ago — and now it is opensource! Not only you can grab the files here — but there is also an instructive video (see link in readme) how to deploy and setup them on a free hosting (while free, it is not as bad — we use it for years for interactive problems).
https://github.com/codeabbey/src — CodeAbbey Opensource
What is inside?
It is not in ACM/ICPC style — rather submissions are (mainly) judged by the correct answer (if you participated in Facebook Hackercup, you know it is not as bad approach — allows to solve problems in any language). Consequently the site is quite light-weight and can run for years on a free hosting. You can add sandbox for running the code optionally (main site uses this also for some language-specific problems).
There are no short-lived contests, rather problems exist continuously and there is a global ranking users table.
Additionally there is a way to create "challenge" problems which are not judged binary (ok/fail), but may be solved better or worse — thus you can create small competitions on a larger problems (somewhat resembling long forgotten topcoder-marathon or yandex-mathematics).
Problems' checking code could be written in whatever language your chosen web-hosting supports. By default it is PHP obviously, with Python and Perl provision out of the box (though generally free hosting won't give you many options).
There are still some minors features to be added from the code of the main site to the opensource version, but the whole main functionality is, well, just ready-to-use. As the school year is starting, you may find it useful for setting up training grounds for your colleagues, candidates etc.
Innovative!