Typical Monster Dexterities

Initiative in the Blue Book rules is determined by dexterity. Holmes suggests rolling a monster's dexterity on the spot if it is not known, and the Sample Dungeon does not include dexterity in the monster stats. However, in the first printing of the module B2 Keep on the Borderlands, Gary Gygax provided a dexterity score for most of the monsters. These can be used to extrapolate some typical monster dexterity scores as envisioned by Gygax:

Non-Humanoid (fastest to slowest):
Puma - DX 18
Adder - DX 15
Medusa - DX 14
Giant Centipede - DX 13
Spider, Large - DX 12
Gray Ooze - DX 11
Skeleton - DX 11
Owl Bear - DX 10
Stirge - DX 10
Huge Dog - DX 9
Fire Beetle - DX 9
Giant Rat - DX 8, 12 (l)
Wight - DX 7
Zombie - DX 6
Gelatinous Cube DX 5

Humanoid (smallest to largest):
Kobold - DX 13 (m), 10 (f), 12 (l)
Goblin - DX 11 (m), 10 (f), 13 (l)
Orc - DX 10 (m), 12 (f), 12 (l)
Hobgoblin - DX 10 (m), 12 (f), 15 (l)
Gnoll - DX 9 (m), 8 (f), 11 (l)
Lizardman - DX 10 (m), 9 (f)
Bugbear - DX 8 (m), 8 (f), 8 (l)
Ogre - DX 8
Minotaur - DX 12

Notes: (m) male, (f) female, (l) leader. 

Numbers represent predominate dexterity, rather than an average. 

A different way to generate a quick DX score is to divide the monster's Move score by 10. I was curious about how well this would match up with the DX stats from B2. So here are the same monsters using the movement in the Holmes rulebook converted to DX by this method:

Non-Humanoid (fastest to slowest):
Puma - not in Holmes Monster List; B2 doesn't give MV; Displacer Beast DX 15
Adder - not in Holmes Monster List; B2 doesn't give MV
Medusa - DX 9
Giant Centipede - DX 15
Spider, Large - DX 6 / 15 (web)
Gray Ooze - DX 1
Skeleton - DX 6
Owl Bear - DX 12
Stirge - DX 18
Huge Dog - not in Holmes Monster List; B2 doesn't give MV; War Dog DX 12 in MM
Fire Beetle - DX 12
Giant Rat - DX 12
Wight - DX 9
Zombie - DX 12
Gelatinous Cube DX 6

Humanoid (smallest to largest):
Kobold - DX 12
Goblin - DX 6
Orc - DX 9
Hobgoblin - DX 9
Gnoll - DX 9
Lizardman - DX 6 / 12 (water)
Bugbear - DX 9
Ogre - DX 9
Minotaur - DX 12

A few are similar, but most are quite different. So Gygax wasn't terribly influenced by the movement rates when determining the DX scores in B2. Some may have been randomly rolled, though others like the Puma were clearly selected, and humanoids seem to follow a trend of decreasing DX scores with increased size (except for the Minotaur). 

Originally posted here. 

Edit: And here are Gygax's typical Strength scores for humanoids, from the 1E DMG, pg 15:

Halfling - 8
Kobold - 9
Human, Gnome, Goblin - 10
Elf, Orc - 12
Dwarf - 14
Hobgoblin - 15
Gnoll - 16
Bugbear - 17
Ogre - 18
Trolls - 18+
Giant - 19 & up

2018 Update: 
There's a case to be made that Skeleton and Zombie Move stats should be reversed in Holmes Basic, so that Skeletons move at 12", Zombies at 6". This is the scores they have in the Monster Manual. If so, the B2 DX scores are a much closer fit to their MV scores.