Ruby

Variables

• Numbers
  
• Strings
• Arrays
• Hashes
• Ranges
• Converting data types
  
• Misc

Language

• Operators
• Boolean expressions
• Statements
• Conditionals
• Loops
• OOP
• Comments

Input / output

• Standard input / output
• File access

Advanced

• Exceptions
• Iterators
• Pattern matching
  

Programs

• CGI
  
• Scripts

Misc

• Misc