In my own blog I wrote a series of articles about how major machine learning classifiers work, with some visualization of their decision boundaries on various datasets.

• Machine learning for package users with R (0): Prologue
• Machine learning for package users with R (1): Decision Tree
• Machine learning for package users with R (2): Logistic Regression
• Machine learning for package users with R (3): Support Vector Machine
• Machine learning for package users with R (4): Neural Network
• Machine learning for package users with R (5): Random Forest
• Machine learning for package users with R (6): Xgboost (eXtreme Gra...
• What kind of decision boundaries does Deep Learning (Deep Belief Ne...

This series of the articles has a simple goal; to help many people understand an algorithm and theoretical features of each ML classifier easily. I believe visualization is the most important in particular.