Speaking the notes
A great way to develop your chest notes is to speak the tones, rather than sing them. This exercise has helped me a lot to develop my chest voice. It helped me to stop singing with head voice in the 4th octave.
*Aaron's note: This definitely ties in with one of my recent singing tips, on getting people to sing like a tone deaf person. usually a 'tone deaf' person sings like they are speaking, so, well done you! Speaking notes definitely would help to thicken the chest voice.