They opened it up to all of 2012. And I looked.
Sheepishly I noticed that I didn't post a single OSR/OGL monster in 2012. Plenty for other systems, but nothing an OSR book would need.
So here is one of mine from "The Witch".
All text that follows is considered Open under the OGL. Full OGL text is listed here, OGL Declaration/Statement.
Armor Class: 2 
Hit Dice: 9d8+2** (43 hp)
No. of Attacks: 2 claws, 1bite
Damage: 1d4+2 / 1d4+1
Special: Blood drain, captivating dance, dying words, spell-like abilities, vulnerable to iron
No. Appearing: 1-3
Saves As: Fighter 9
Alignment: Chaotic (Chaotic Evil)
The Baobhan sìth (bavaan shee, “faerie woman” in Scottish Gaelic) are evil female fey that feed on the blood of living creatures. By entrancing creatures with their dance, they lure men to their deaths. Baobhan sìth are always female; no males of this race are known to exist. These creatures are generally found in remote locations such as unclaimed forests or overgrown and ruined keeps, castles or the like; always a secluded location, but close enough to a populated area that the baobhan sìth can feed when hungry.
Often called the “White Woman” of the Scottish Highlands, the baobhan sìth are often confused with vampires. Though they are not undead, they do have a lot of similarities. Both feed on blood and use seduction in order to lure their prey into their grasp. Baobhan sìth also are vulnerable to cold iron, much like a vampire to silver. The baobhan sìth also avoids bright sunlight, it is not dangerous to her, but they avoid it all the same.
Local legends claim that when young women fall to the allure of witchcraft and lie wantonly with men they will die and return as baobhan sìth.
Their lairs are typically clean; the monsters have disposed of the rotting corpses of past victims. They are solitary creatures and rarely work in groups. There is however a popular tale of a group of four men traveling in the Scottish Highlands that were seduced and attacked by three or four (depending on the tale) Baobhan sìth working together. Baobhan sìth each have their own hunting ground and to intrude on another’s is certain death.
Baobhan sìth prefer to use their abilities against male humanoids, particularly elves or humans, and most of all bards. They generally avoid dwarves and halflings, though if food is scarce they have no qualms about draining the blood of just about any living creature. They do not drink the blood of animals; no matter how hungry they are, as they see this as primitive and savage.
A baobhan sìth stands 5 to 5-1/2 feet tall and weighs roughly 120 pounds. Her hair ranges in color from black or brown to golden yellow. Eye color varies but is usually brown or green. A baobhan sìth wears flowing, loose fitting robes or tunics of white or green often tied at the waist with a scarf of red or black.
They speak Common, Elven, and Sylvan.
A baobhan sìth prefers to attack a lone target and generally avoids combat with groups, fleeing if confronted by such a party. Stragglers are often the subject of the baobhan sìth’s attention if the straggler is far enough behind its comrades.
When first encountered, a baobhan sìth opens combat with her captivating dance. Creatures that fail to succumb are entangled (saving throw vs. Paralysis). Once she has captivated at least one foe, she moves in and uses her sharp nails to draw blood from the victim’s chest or throat and then it drains the victim’s blood. It deals bite damage and drains blood, dealing 1d4 points of permanent Constitution drain each round it maintains the hold. At Constitution 0, the victim dies.
The Baobhan Sìth may cast spells as a 3rd level witch.
If overwhelmed or outnumbered, the baobhan sìth uses her entangle ability (if she hasn’t already used it) and tries to slip away into the surrounding forest.
Leanan Sìth (Leanan Sídhe, Lhiannan Shee, “faerie mistress”): The Leanan Sìth is the Manx (Isle of Man) counterpart to the Baohbhan Sìth. This creature can be found all across the British Isles. She has the additional power of being able to turn invisible at will, as a spell like ability (9th level). The Leanan Sìth will typically feed on the blood and life force of young poets. They drain the victims slowly, and in a state of ecstasy. Such poets create works of unsurpassed brilliance while in the clutches of these women.
Section 15 Copyright Notice
Open Game License v 1.0a Copyright 2000, Wizards of the Coast, Inc.
System Reference Document Copyright 2003, Wizards of the Coast, Inc.; Authors Jonathan Tweet, Monte Cook, Skip Williams, Bruce R. Cordell, based on original material by E. Gary Gygax and Dave Arneson.
Liber Mysterium: The Netbook of Witches and Warlocks is Copyright© 2003, Timothy S. Brannan and the Netbook of Witches Team.
Basic Fantasy Role-Playing Game Copyright © 2006-2008. Chris Gonnerman.
Labyrinth LordTM. Copyright © 2007, Daniel Proctor. Author Daniel Proctor.
"Baobhan Sìth" Copyright ©2012, Timothy S. Brannan