Alguma das outras duas maldições imperdoáveis foi usada durante o curso dos sete livros?

Sim, em ambos os casos. (Spoilers for post-GoF)

Maldição Cruciatus

A maldição Cruciatus é usada por Harry em Bellatrix Lestrange, enquanto ela foge do Departamento de Mistérios em Ordem da Fênix :

Hatred rose in Harry such as he had never known before; he flung himself out from behind the fountain and bellowed, “Crucio!”

Bellatrix screamed: the spell had knocked her off her feet, but she did not writhe and shriek with pain as Neville had - she was already back on her feet, breathless, no longer laughing. Harry dodged behind the golden fountain again. Her counter-spell hit the head of the handsome wizard, which was blown off and landed twenty feet away, gouging long scratches into the wooden floor.

“Never used an Unforgivable Curse before, have you, boy?” she yelled. She had abandoned her baby voice now. “You need to mean them, Potter! You need to really want to cause pain – to enjoy it – righteous anger won’t hurt me for long – I’ll show you how it is done, shall I? I’ll give you a lesson—”

Isso é depois que Bellatrix matou Sirius, o único membro restante da família de Harry, então ele está compreensivelmente zangado.

Se isso não conta, então o Bellatrix também o usa no Neville na mesma luta:

Bellatrix raised her wand. “Crucio!”

Neville screamed, his legs drawn up to his chest so that the Death Eater holding him was momentarily holding him off the ground. The Death Eater dropped him and he fell to the floor, twitching and screaming in agony.

Maldição Imperius

A maldição Imperius é usada (também por Harry) quando o trio invade o banco Gringotts. Na época, um dos goblins está prestes a explodir sua capa, então Harry precisa impedi-lo de fazer isso. (Neste ponto, o trio foi marcado criminosos, e disfarçado.)

Harry raised the hawthorn wand beneath the cloak, pointed it at the old goblin, and whispered, for the first time in his life, “Imperio!”

A curious sensation shot down Harry’s arm, a feeling of tingling warmth that seemed to flow from his mind, down the sinews and veins connecting him to the wand and the curse it had just cast.

Existem muitos outros casos em que as maldições são usadas ao longo dos livros (e filmes), mas esperamos que os dois exemplos acima sejam suficientes para mostrar que sim, todas as três maldições foram usadas.

Também Barty Crouch, SR manteve Barty Crouch, JR sob maldição imperiosa depois de quebrá-lo de Azkaban.

Draco Malfoy manteve Madame Rosmerta sob o comando de Imperious quando empreendeu sua "tarefa" de matar Dumbledore.

Harry também usou o cruciatus em Amycus Carrow (com sucesso, contra quando ele tentou em Bellatrix Lestrange)

Sim, em O Cálice de Fogo , a maldição Imperius é usada em Viktor Krum na terceira tarefa do Torneio Tribruxo.

He's too late, she's [Fleur Delacour] disappeared. He [Harry] sends up a red spark into the air. A heavy wind starts blowing, walls are closing in, Harry runs. Harry sees something shining in the distance and he moves towards it Viktor tries to zap him but misses.

CEDRIC: Get down!

Harry ducks and Viktor gets zapped by Cedric. Cedric runs up and kicks the wand out of Viktor's hand. He points his wand at Viktor's body as if to finish him off, Harry runs up and intervenes.

HARRY: No stop! He's bewitched, Cedric. (source)

A Maldição Cruciatus é usada em Harry pouco depois de Voldemort matar Cedric.

Voldemort raised his wand, and before Harry could do anything to defend himself, before he could even move, he had been hit again by the Cruciatus curse. The pain was so intense, so all-consuming, that he no longer knew where he was... white-hot knives were piercing every inch of his skin, his head was surely going to burst with pain; he was screaming more loudly than he'd ever screamed in his life — (source)

Harry tenta usar a Maldição Cruciatus em Bellatrix Lestrange depois que ela mata Sirius em Ordem da Fênix .

Hatred rose in Harry such as he had never known before: he flung himself out from behind the fountain and bellowed, "Crucio!"

Bellatrix screamed: the spell had knocked her off her feet, but she did not writhe and shriek with pain as Neville had – she was already back on her feet, breathless, no longer laughing. [...]

"Never used an Unforgivable Curse before, have you, boy?" she yelled. She had abandoned her baby voice now. "You need to mean them, Potter! You need to really want to cause pain – to enjoy it – righteous anger won't hurt me for long – I'll show you how it is done, shall I? I'll give you a lesson —" (source)

As Maldições Imperdoáveis são usadas no Capítulo 14 em Cálice de Fogo (por Barty Crouch Jr.) nas aranhas, e depois disso, todas as três são usadas pelo menos uma vez. Por exemplo, em Ordem da Fênix, Bellatrix mata Sirius com a Maldição da Morte, e Harry usou a maldição Cruciatus nela. No entanto, a Maldição Imperius não é usada novamente até as Relíquias da Morte, quando Harry a usa para ajudá-las a invadir Gringotes. Mas, para responder à pergunta, sim, todas as três Maldições Imperdoáveis são usadas no cânon.

Sim, existem inúmeras contas de ambos os feitiços usados nos livros, bem como nos filmes

Para uma lista completa, consulte estes artigos na wikia da HP: link link