Hi Andres,
Below are the useful links to XBlock tutorials/documentation -
1. This
video will give you overview of XBlocks (I am not sure if everything in the video is still relevant, but you will get a clear, conceptual picture for sure)
2. "hello World" kinda XBlock tutorial I followed is
here.3. XBlock docs are cool and you can find about the APIs
here4. Yet another great site is
The XBlock Directory . Also, click
here to get yet another Xblock directory. Best way to learn about the same would be to look in the code of those XBlocks.
Hope this gets you started.
- Utk.