Fig, Olive Oil and Sea Salt Challah (This is, with minor modifications, the recipe I use most — sans the figs.)
http://smittenkitchen.com/blog/2012/09/fig-olive-oil-and-sea-salt-challah-book-tour/
 
Sweet Challah (This is an excellent 3-cup recipe)
http://www.myrecipes.com/recipe/sweet-challah
  
Adventures in Challah Blog (lots of variations):
http://adventuresinchallah.com/
 
Inside the Jewish Bakery: Recipes and Memories from the Golden Age of Jewish Baking,
by Stanley Ginsberg and Norman Berg
 
I haven't tried this recipe yet, but she's very convincing and it sure sounds good. http://thefarmbarbie.com/the-best-challah-bread/
 
 
Videos

Note: there are a lot of six-braid instructions on the web, most of which are incomprehensible. Try these first:

Yesh (Six-braid technique a la Rivka Malka)
https://www.youtube.com/watch?v=CzHfLwNERMc
 
Rivka Malka (Adorable, spiritual, frum woman makes challah a spiritual experience)
https://www.youtube.com/watch?v=NwpWsMuVQ6M
https://www.youtube.com/watch?v=0dSaIPHGrfg (really good 6-braid instructions — “2nd one over, 1st one in the middle”)
 
Dovber Berkowitz (Slo-mo six-braid (to the tune of Let It Be!)  — skip the first minute!)
https://www.youtube.com/watch?v=FQ64m76BrN4#t=204.901
 
Leah (She’s a pro)
https://www.youtube.com/watch?v=NyprANiynyQ (part 1 mixing dough)
https://www.youtube.com/watch?v=3vnpxlXZclA (part 2 shaping challah rolls)
https://www.youtube.com/watch?v=bA0YJSx_lrg (part 4 braiding 4 & 6 strands)
 
Jamie Geller (Oy, just watch her!)
https://www.youtube.com/watch?v=mT-diEkKAX8
 
Titli Nihaan (She’s a real hoot! — amazing braiding instructions — 3,4,5,6,7,8,9 braids):
https://www.youtube.com/watch?v=RP6j7esQyjk#t=15.879254
 
Extraordinary Israeli braider! (You gotta see it to believe it!)
https://www.youtube.com/watch?v=RblfXecu9lo
 
Braided Windsor Knot (Pretty trippy)
https://www.youtube.com/watch?v=ZiicwhL74RU

Nutella star (I do 12 cuts, not 16, creates a six point star):
https://www.youtube.com/watch?v=HwvYmBo_bN4
 

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