Mary's Bracelet
In 4.03 In The Beginning, Mary Campbell is seen wearing a charm bracelet. The charms have various mystical significance, allowing Dean to identify her as a hunter. There are at least six, probably eight to ten, charms; the charm to the right of the pentagram is some sort of human figure, possibly a Buddha or Kwan Yin, and the two charms to the left of the hexagram are small and the one just left of the hexagram is round.
Unicursal Hexagram
The unicursal hexagram is a six-pointed star that, unlike the Star of David, can be drawn in a single line. It is a common symbol of Thelema, the religion founded by Aleister Crowley (who is of course referenced in the names of the demons Alastair and Crowley, and is probably a protective symbol.
Cross
The cross is the most common symbol of Christianity. It is definitely a protective symbol, though vampire lore holds falsely that the cross deters vampires.
Pentagram
The pentagram was originally a Mesopotamian protective symbol and has since been coopted by the Wiccans; when inscribed inside a circle, it is called a pentacle. Some devil's traps use pentacles. Inverted, the pentagram is a Satanic symbol.
