CodingBat is a website that allows one to flex their coding muscles through simple yet effective exercises. Currently, it offers exercises in Java and Python. One really great aspect of this website is that all the coding is done from the browser. No need to download compilers or IDE's. You can get started right away upon creating your free account. In addition, it saves your solutions in case you want to go back later to review them. It also has a nice reporting feature that allows the sharing of solutions with another user(For example a student and professor). In case the exercises on the site are not adequate enough, one can also create custom exercises.
On a more personal note, it would have been nice and useful to have this site around years ago when I was learning how to program.
