Mr Ollivander: Rowling gives a lot of background information not only about Garrick Ollivander, the current proprietor of the shop in Diagon Alley, but also about his famous wand-making family.
Wand Woods: Rowling lists many wand woods and their qualities.
Wand Lengths & Flexibility: Rowling writes about the qualities of wands and how they are related to the personalities of the user.
Wand Cores: Rowling writes from Garrick Ollivander’s notes about the three Supreme Cores.
Calendar and Dates
382 B.C. -- when the Ollivander family first started selling wands
Interesting facts and notes
Phoenix feather wands "show the most initiative, sometimes acting of their own accord..." c.f. DH4
"However, abnormally short wands usually select those in whose character something is lacking, rather than because they are physically undersized (many small witches and wizards are chosen by longer wands)." This seems to be applicable to Umbridge, whose wand was unusually short: " Professor Umbridge opened her handbag, extracted her own wand, which was an unusually short one, and tapped the blackboard sharply with it..." (OP12)