The Katha relates the education of Nakiketas and the Aitareya tells the story of the celebration after Indra killed the demon Vritra.  
The first Khanda of the Mundaka begins with Brahma's distinction between "higher" and "lower" knowledge.  The Svetasvatara contains such maxims as, "With collected minds we are at the command of the divine Savitri, that we may obtain blessedness."  The Katha relates the education of Nakiketas and the Aitareya tells the story of the celebration after Indra killed the demon Vritra.  Famously translated by Max M?ller, this text's first part is the Khandogya, which calls on humans to meditate on the syllable "Om."  FTP, identify this collection of sacred Hindu texts often considered the fifth part of the Vedas.
The first Khanda of the Mundaka begins with Brahma's distinction between "higher" and "lower" knowledge.  
Upanishads