Here is a general summary of most the Great Houses mentioned in-game and in Lore NOTE: There are possible spoilers for the in-game main quest.
House Hlaalu: As a result of its close relationship with the Imperial administration, House Hlaalu has emerged as politically and economically dominant among the Great Houses of Vvardenfell and Morrowind. Hlaalu welcomes Imperial culture and law, Imperial Legions and bureaucracy, and Imperial freedom of trade and religion. Hlaalu still honors the old Dunmer ways -- the ancestors, the Temple, and the noble houses -- but has readily adapted to the rapid pace of change and progress in the Imperial province.
House Redoran: The Redoran prize the virtues of duty, gravity, and piety. Duty is to one's own honor, and to one's family and clan. Gravity is the essential seriousness of life. Life is hard, and events must be judged, endured, and reflected upon with due care and earnestness. Piety is respect for the gods, and the virtues they represent. A light, careless life is not worth living. Redoran settlements are designed in the Dunmer village style, built of local materials, with organic curves and undecorated exteriors inspired by the landscape and by the shells of giant native insects. Redoran villages are typically centered on Temple compounds and their courtyards, with huts and tradehouses gathered around a central plaza, as in the West Gash village of Gnisis. Ald'ruhn, the Redoran district seat, is exceptional, with its distinctive feature being the colossal prehistoric bug shell that has been adapted as the house's council house. The main focus of House Redoran is maintaining the traditions of the settled Dunmer and, more specifically, the way of the warrior. Due to this focus, the native Tribunal Temple is a natural ally. There is also mutual respect between them and the Imperial Fighters Guild and Imperial Legion. They have less respect for the other Imperial Guilds (i.e. Mages Guild and Thieves Guild) and the Imperial Cult religion.
House Telvanni: Traditionally isolationist, most House Telvanni of Morrowind wizard-lords pursue wisdom and mastery in solitude. But certain ambitious wizard-lords, their retainers, and clients have entered whole-heartedly into the competition to control and exploit Vvardenfell's land and resources, building towers and bases all along the eastern coast. The Telvanni think that wisdom confers power, and power confers right. House Telvanni is among the staunchest defenders of slavery, which they saw as an ancient Dunmer right. House Telvanni are, therefore, strong enemies of abolitionists.
House Indoril: the Indoril are orthodox and conservative supporters of the Temple and Temple authority. House Indoril is openly hostile to Imperial culture and religion, and preserves many traditional Dunmer customs and practices in defiance of Imperial law. It is one of two houses without formal holdings on the Vvardenfell District and is generally regarded to be in the decline due to their staunch opposition of Imperial control.
House Dres: House Dres is one of two houses without holdings or interest in Vvardenfell. Dres District is in the south of Morrowind, bordering the swamps and marshes of Black Marsh. House Dres is an agrarian agricultural society, and its large saltrice plantations rely completely on slave labor for their economic viability. Always firm Temple supporters, House Dres is hostile to Imperial law and culture, and in particular opposed to any attempts to limit the institution of slavery.
House Dagoth: House Dagoth is the "lost" Sixth House. In the First Age, House Dagoth betrayed the other Great Houses during the War of the First Council, and was destroyed for their treason. The House briefly reappeared in Vvardenfell c. 3E 400. The resurgent House Dagoth was all of what remained of the ancient, and now defunct, Sixth Great House of the Chimer, headed by the demi-god Dagoth Ur and enemy of the Almsivi Tribunal. Dagoth Ur recruited followers by manipulating and controlling their dreams. Corprus disease appeared in these 400 years, pioneered by House Dagoth. Blight storms progressively began to ravage more and more of Vvardenfell during this period. The growth of blight storms was practically exponential, posing a massive threat to the people of Vvardenfell. It (House Dagoth) was destroyed shortly thereafter by the Nerevarine. Dagoth Ur attempted to create a new god, Akulakhan, to conquer Tamriel. Their primary bases lay within Red Mountain, in the ancient Dwemer crater citadels.
House Dwemer: the Dwemer, the "people of the deep", are a fabled "Lost Race" of Mer from Dwemereth, which mostly consisted of modern-day Morrowind, where they are believed to have been the most prolific, Many misconceptions about them have abounded for centuries. In reality however, they are best described as having been fearsome, unfathomable, and even cruel, though also careful, intelligent, and industrious. Their society consisted of free-thinking yet reclusive clans devoted to the secrets of science, engineering, and the arcane until they mysteriously disappeared around 1E 700, supposedly during the apex of The War of the First Council.
House Sotha: House Sotha was a minor house based in the city of Ald Sotha, birthplace of Sotha Sil. It is said that the city and the house were both destroyed by Mehrunes Dagon. The only one who survived the destruction of the House by Dagon was Sotha Sil, who was rescued by Indoril Nerevar and later became one of his most trusted advisers and later one of the three gods and leaders of the Almsivi Tribunal.
House Mora: House Mora was a minor house, best known for having the Ra'athim clan (also spelled Ra'Athim and R'Aathim) as their members. They were later adopted into House Hlaalu. They gave Morrowind and Tamriel several proficient rulers, such as Queen Barenziah, King Moraelyn, and Empress Katariah.
You may be wondering as to why I decided to include minor houses as well as houses whose status was a formality (like the resurgent House Dagoth or House Dwemer), the main reason being to allow for greater freedom of choice, even to those who especially like in-game lore such as myself.
Also feel free to point out if I made any mistakes regarding the Houses, this is after all a wide-ranging topic and I will take criticism graciously. And just because there is a poll here doesn't mean your not allowed to post, quite the opposite in fact.
P.S I only placed the summaries there to refresh your memories and give general points, you don't have to base your opinion off that. Also thanks to UESP Wiki and the in-game book "Great Houses of Morrowind" for helping out in finding the houses and their general information. I also realize that there is another poll like this topic, the only reason I decided to do this was the lack of variety found in the other (no offense intended to the author).
