Infants are typically ready for solids around four months old, when they have good head and neck control and can sit up with support. Aside from talking to a pediatrician, here are several resources that will help kick off the occasion.
Online Resources
Wholesome Babyfood
Gerber
Kidcentral TN
Your Kids Table
Book Resources
Food Fights by Laura A. Jana and Jennifer Shu
The Picky Eater Project by Sally Sampson and Natalie Digate Muth