Learning Digital Signal Processing [closed]

Answer 1

How Do I Learn DSP?

A Beginner's Guide to Digital Signal Processing

As well as the The Scientist and Engineer's Guide to Digital Signal Processing By Steven W. Smith, there is also the excellent Understanding Digital Signal Processing

Answer 2

I learned a lot from the Scientist and Engineer's Guide to DSP. You can read it for free online at http://www.dspguide.com/ It's nice because it focuses more on what you can do with DSP, rather than the underlying math.