Below I have listed some good resources that you can use to learn and practice your Ruby skills. They are not in specific order, but if you have no Ruby experience I'll suggest the CodeCademy for your first try.
It's a really cool and beginner friendly course which you can learn a lot in a short amount of time.
An online book which contains fifty-two exercises.
This is one of my favorites. RubyMonk teaches Ruby in four different level courses, and each course contains its own exercises.
It's a challenge website, but it also has a specific domain, where you would learn Ruby in a challenging way.
A website with loads of interesting Ruby problems.
This website uses the TDD approach to teach Ruby.
This website also has TDD approach for teaching. But the cool thing about the website is that, after giving your solution, you can see how other people solved the same problem. You can also exchange ideas about a solution.
Another cool challenge website, where challenges are named "katas" and you can collect points by solving them.
Ruby Monday is an online meetup by Codenewbie which helds every Monday, and this is where you can find cool people. You can discuss Ruby problems comfortably in the video conferences, since they are very nice to newbies. By attending Ruby Monday you will learn a lot.