Each Maia followed a Valar . And from them inherited both skills and traits. They are numerous, and not all named, but the more famous ones are:
He is the chief and most powerful of the maia, he is the standard-bearer of Manwe and is as powerful as some of the Valar. He is known as "The Greatest With Arms" amongst both Valar and Maiar. He is prophesised to aid Manwe in defeating Melkor upon his return from the void. It was he who led the great host from Valinor to utterly destroy both Melkor and his armies during the war of wrath.
She is also the chief of the maia, she is a maia to Varda, queen of stars. She is not a main character during the series, and is only referred to and mentioned, rather like her valar, rather than actually performing deeds.
He is a maia to Aule the smith. He was greatly skilled and volunteered to lead the Istari to Middle-Earth to combat his fellow maia Sauron. After departing from Valinor he was forbidden from returning due to his disobediance regarding not using his full power in Middle-Earth.
Most Famous of the Valar. He is maia to Manwe and Varda, however often spent time with Nienna the weeper from whom he learnt pity and patience. He was chosen by Manwe personally to go alongside the Istari to Middle Earth as Manwe foresaw his future strength. He is re-incarnated by Eru after defeating a Balrog atop Zirak-Ziragil. Ultimately, he is the only maia to return from middle earth. He also is the only non-elf to ever wield a elven ring(the ring called Narya...Ring of Fire)
He is almost as famous as Gandalf. He was originally maia to Aule, and used the skills he acquired there later (getting the elves to forge the rings of power, forging one ring by self, refining the trolls and Orcs etc,) he was corrupted by Melkor and joined the Dark Lord in Middle Earth. He caused many wars and was one of the most powerful amongst the maia. He was notorious for his cunning and guile.
All Balogs are the maia of Melkor, who created them through the discord he created in the Ainur. They are terrible fiery demons, and are small number but difficult to defeat. Most notorious is Gothmog who served under Melkor during the War of Wrath, his power and martial prowess is said to have exceeded Sauron's. The last one recorded was known as Durin's Bane and was killed by Gandalf towards the end of the 3rd age.
He was one of the less powerful maia, however was renowned for his love for nature. He was a maia to Yavanna. After arriving in Middle Earth he did very little save learn from and teach the Sindarin elves of Mirkwood his skills and lore. Also gaining the respect of Beorn.
The greatest of the spiders, she sapped the life of the Great Trees and poisoned them. After this, she nearly succeeded in killing her master, the most powerful of the valar: Melkor. Had it not been for the intervention of the Balrogs she would have succeeded. Her last child is Shelob, who is defeated during the War of The Ring by the hobbit Samwise Gamgee with the aid of the light from Galadariel, though it's not known if she died from her wounds or not.