IMHO:
PC race is: Human
That really simplifies your world. Use some Human NPCs for fights, too. Without Half-Orcs & Half-Elves, you're free to cut or change those races.
1/ Goblinoids: typical "evil" race, and you get three for the price of one -- goblin, hobgoblin, bugbear. If you want to make your LotR addicted players happy, mention that they're also called "goblins", "orcs" and "uruk-hai".
2/ Wolves: goblins ride them, druids tame them, and they illustrate Tripping
3/ Rats -- Dire Rats & Rat Swarms: illustrate Disease and Swarm mechanics, respectively
4/ Horses -- people ride them
5/ Fey: Pixies (DR, invisibility) and Dark Elves (in fact, they're the ONLY elves, but they don't much care for humans and use drow stats. Illustrate SR, spell-like abilities, how much fun it is to kill elves.)
6/ Magical Beasts: Ankheg, Hippogriff, Griffon, Manticore, Owlbear -- stick to the classics
7/ Undead: Skeletons, Ghouls, Shadows. Illustrate DR, Fort saves, and incorporeality + ability damage (respectively). See below for why no Zombies.
8/ Outsiders: Imp, Quasit, Kyton, Babau, Hound Archon, Lantern Archon, Howler, Salamander. All of these should be RARE.
9/ Aberrations: Ettercap, Grick, Rust Monster, Will-o-Wisp.
10/ Elementals: Just the core 4 (air, earth, fire, water) in various sizes.
11/ Giants: Trolls. That's it. Reach, Rend, Regeneration -- who needs more?
12/ Oozes: Grey Ooze and Gelatenous Cube fill the niche nicely.
13/ Monstrous Humanoids: Hag, Harpy, Minotaur. These really cover the bases of spells, special abilities, and just a melee monster. They're also easily recognized -- no need to justify their existance, unlike a Grick (for example).
14/ Vermin: pick one that's native to your campaign area -- spiders, scorpions or centepedes. Illustrates poison and mindless-yet-living critters.
15/ Dragons: Just use Fire dragons. Alignment is individual -- you can't judge a drake by his scales, as they say. (You can judge him by whether he incinerated a whole village, though.)
16/ Constructs: animated objects are a staple of fantasy, and underused even in Core D&D. Consider changing "Summon Monster N" to "Animate Object N", which animates an object of the same CR as the monsters it would have summoned, but you have to pick a specific object that's in the scene to animate. They scale in size & CR, and illustrate Hardness.
NO ZOMBIES -- Skeletons do everything that Zombies do (damage-type DR, cheap, nice for Clerics to blast), but they don't require special movement & attack rules. Special rules are bad.
Anyway, that's my opinion of a fully-functional reduced monster palette.
-- N