Another tidbit from JKR's site (semi-spoiler)

[Ceridwen]

Carol:
> BTW, does anyone think that the lightning bolt might be
> a Sowilu rune? Compare the picture revealed by Peeves on the Links
> page with this:
> 
> http://www.bewitchingways.com/runes/runes.htm

Ceridwen:
Definitely Sowelu.  Sound: S.  Means: Sun.  Two Sowelus, the tail of 
the top one and the head of the bottom, could form the scar very well.
> 
> I always thought the scar was an Eihwaz rune because of the symbolism
> and Hermione's reference to missing that question on her OWL, but this
> one's a better match in terms of shape. And "Ancient Runes Made Easy"
> suggests that runes will be important in Book 7. (Of course she's been
> taking that class for a plot reason!)

Ceridwen:
The runes in Ancient Runes Made Easy are not like any Runes I've seen.  
They're definitely Potterverse runes.  Doesn't 7 remind you of a 
sleestack?

Ceridwen.