The Biblical Archeology Review has an article on how the alphabet was born from Egyptian hieroglyphs.
The article focuses on the Serabit El Khadem site in Sinai, and the inscriptions found in the temple of Hathor there.
Lot ts of good detailed pictures of the inscriptions. Check the 2 side bar articles as well. One is about Wadi El Hol inscriptions, the other is about an Ugaritic cuneiform alphabet.