Let's see...I believe these are most of the Maiar enlisted with Melkor/Morgoth, not bred by him.
-Gothmog, Lord of the Balrogs and Captain of Angband
-Ungoliant the great spider, devourer of light
-other Balrogs
-and of course, Sauron
There are, of course, many other forces of Evil, but couldn't necessarily be considered as Maiar like...
-Watchers (various)
-Fellbeasts
-Wereworms of the East
-Great Spiders
-Ordinary Wolves like Carcharoth
-heh..Tevildo the Cat.
I'm not sure whether these are Maiar or not:
-Thuringwethil the Vampire, the "Lady of Shadow"
-other Vampires
-Drauglin the Werewolf, Lord of Tol-in-Gaurhoth
Ungoliant may have been a Maia, but we cannot tell for sure from the brief description. All we really know is that, according to Elf legend, she crept into Arda from the darkness outside (I don't have my books handy, so I can't give the exact quote).
Dragons are said to have been created by Morgoth, but they may have been inhabited by Maia spirits, since Morgoth (as with all the Valar) could not create sentient life himself. Much the same, I should imagine, goes for Vampires and Werewolves.
I would doubt, however that Watchers were Maiar. They seem far more like beasts and, as such, are more likely to have been created and/or corrupted by Morgoth. And as for the great Spiders, even if Ungoliant was a Maia, I very much doubt that her Arda-born offspring would have been.
I'm not sure about the Werewolves, since apparently they were technically bred by Morgoth. Not like orcs, but similar. The werewolves were...
"Werewolves, fell beasts inhabited by dreadful spirits that he (Sauron) had imprisoned in their bodies."
The Silmarillion, "Of Beren and Luthien"
Then again, it could have been Maiar spirits that inhabited their bodies, it could also have been different.
About Vampires, Christopher Tolkien, in one of his notes I tracked down, speculates that "Vampires like Thuringwethil, being thus able to transform into a bat-like creature and fly aloft, were presumably Maiar or some such being." Also, both the Encyclopedia of Arda and Atlas of Middle-Earth (at least relatively respectable volumes of Tolkien, but not written by him) state that the Vampires either were Maiar, or something close to being Maiar.
At the end, we are not sure whether the Vampires and the Werewolves are Maiar or not.
The only Maiar that we can say for sure were persuaded by Morgoth to his cause are, Sauron and the Balrogs. Of the Balrogs, only Gothmog was named, although there are others individually identified (Durin's Bane and the Balrog which Glorfindel (of Gondolin) fought).
As for the other obvious cases, (Orcs, Trolls, Fellbeasts, etc.) I wouldn't explicate them further.