What is the Noble Eightfold Path? Where is the Noble Eightfold Path found in the Pali Canon?  Are there significant differences among the traditions in its interpretation?
According to Magga-vibhanga Sutta: An Analysis of the Path

Now what, is the Noble Eightfold Path? 


Right view


  Knowledge with regard to stress, knowledge with regard to the origination of stress, knowledge with regard to the stopping of stress, knowledge with regard to the way of practice leading to the stopping of stress

Right resolve


  Being resolved on renunciation, on freedom from ill will, on harmlessness

Right speech


  Abstaining from lying, abstaining from divisive speech, abstaining from abusive speech, abstaining from idle chatter

Right action


  Abstaining from taking life, abstaining from stealing, abstaining from unchastity

Right livelihood


  There is the case where a disciple of the noble ones, having abandoned dishonest livelihood, keeps his life going with right livelihood

Right effort


  (i) There is the case where a monk generates desire, endeavors, activates persistence, upholds &amp; exerts his intent for the sake of the non-arising of evil, unskillful qualities that have not yet arisen.
  
  (ii)He generates desire, endeavors, activates persistence, upholds &amp; exerts his intent for the sake of the abandonment of evil, unskillful qualities that have arisen.
  
  (iii)He generates desire, endeavors, activates persistence, upholds &amp; exerts his intent for the sake of the arising of skillful qualities that have not yet arisen. 
  
  (iv)He generates desire, endeavors, activates persistence, upholds &amp; exerts his intent for the maintenance, non-confusion, increase, plenitude, development, &amp; culmination of skillful qualities that have arisen

Right mindfulness


  (i) There is the case where a monk remains focused on the body in &amp; of itself — ardent, aware, &amp; mindful — putting away greed &amp; distress with reference to the world.
  
  (ii) He remains focused on feelings in &amp; of themselves — ardent, aware, &amp; mindful — putting away greed &amp; distress with reference to the world. 
  
  (iii) He remains focused on the mind in &amp; of itself — ardent, aware, &amp; mindful — putting away greed &amp; distress with reference to the world. 
  
  (iv) He remains focused on mental qualities in &amp; of themselves — ardent, aware, &amp; mindful — putting away greed &amp; distress with reference to the world.

Right concentration


  (i) There is the case where a monk — quite withdrawn from sensuality, withdrawn from unskillful (mental) qualities — enters &amp; remains in the first jhana: rapture &amp; pleasure born from withdrawal, accompanied by directed thought &amp; evaluation. 
  
  (ii) With the stilling of directed thoughts &amp; evaluations, he enters &amp; remains in the second jhana: rapture &amp; pleasure born of concentration, unification of awareness free from directed thought &amp; evaluation — internal assurance.
  
  (iii) With the fading of rapture, he remains equanimous, mindful, &amp; alert, and senses pleasure with the body. He enters &amp; remains in the third jhana, of which the Noble Ones declare, 'Equanimous &amp; mindful, he has a pleasant abiding.' 
  
  (iv) With the abandoning of pleasure &amp; pain — as with the earlier disappearance of elation &amp; distress — he enters &amp; remains in the fourth jhana: purity of equanimity &amp; mindfulness, neither pleasure nor pain.