During the RCOMM 2010 , Milan Vukiecevic gave a talk about WhiBo, which is like having a mini-RapidMiner within RapidMiner. They divided well known algorithms like decision trees into their components which can now be almost arbitrarily combined. This allows for the easy development of already known algorithms (like the many different decision tree or k-means variants) but also simplifies the detection of new ones.

Now the authors have translated the WhiBo extension to RapidMiner 5 and published  a first video about how to use the extension:

You can find more information about the WhiBo extension and how you can install it at

http://whibo.fon.bg.ac.rs/joomla/

If you are interested in the paper and other great papers about using RapidMiner and about new extensions, I would like to recommend the conference proceedings of the RCOMM 2010 to you.