> Thanks for your kind reply. I already went through hackety hack. It's so sad that "_why" disappeared all on a sudden on mid-2009.

Hackety Hack maintainer here. Thanks for trying it out, we're gearing
up for another release soon, but I bet you're past where it'd be
helpful now.

The big ones are:

Poignant Guide
Learn to Program by Chris Pine
Learn Ruby the Hard Way
Ruby Koans