Many experts suggest teaching letter sounds along with letter names. Vowel sounds and the sounds for the letters c and g can be tricky since they make more than one sound. Most research I have done suggests teaching the short vowel sounds first and the hard sounds for the letters c and g. The hard sound sound of c is in the word cat. The hard sound of g is in the word goat. The soft sounds are in the words cent and giraffe.
Free Online Letter Learning Websites: Here's a page with links to ten high quality letter learning websites. Alphabet Books: Here's a page with my favorite alphabet books.