List of Interesting Mountains and Volcanoes in Tanzania
TL;DR: Kilimanjaro, at 5,895 meters, is the highest mountain in Africa and the highest free-standing mountain in the world. Ol Doinyo Lengai erupts natrocarbonatite lava, and Ngorongoro is the largest inactive, intact and unfilled volcanic caldera in the world.
These are mountains and volcanoes in Tanzania that are interesting, with the height of each one and what makes it special.
Kilimanjaro, Meru, Lengai and Ngorongoro

Mount Kilimanjaro is 5,895 meters high, that's 19,341 feet. It's the highest mountain in Africa and the highest free-standing mountain in the world. It has three volcanic cones, Kibo, Mawenzi and Shira. Kibo is dormant and its last major eruption was 360,000 years ago. The mountain has its own climate zones, from tropical rainforest down below to arctic ice fields at the top.
Mount Meru is 4,566 meters or 14,980 feet. It's an active stratovolcano in Arusha National Park and it last erupted in 1910. There is a lot of biodiversity, with forests, savannahs and a lot of wildlife.
Ol Doinyo Lengai is 2,962 meters or 9,718 feet. In the Maasai language the name means "Mountain of God". It's an active volcano and it erupts natrocarbonatite lava, which is special because it has a low temperature for lava and is very fluid. When the lava cools it turns white, and the landscape looks surreal.
The Ngorongoro Crater has its caldera rim at 2,286 meters or 7,500 feet. It's the largest inactive, intact and unfilled volcanic caldera in the world. It formed about 2 to 3 million years ago, when a large volcano exploded and collapsed. It's famous for its wildlife, there are a lot of game animals living close together.
Hanang and Loolmalasin

Mount Hanang is 3,417 meters or 11,210 feet. It's the fourth highest mountain in Tanzania and a dormant volcano in the Hanang District. It has a lot of endemic plants and people like to go trekking there.
Mount Loolmalasin is 3,648 meters or 11,968 feet. It's the third highest mountain in Tanzania and it's near the Ngorongoro Conservation Area. It's known for beautiful landscapes and rare plants.
The Southern Highlands and beyond

The Udzungwa Mountains go up to 2,576 meters or 8,451 feet. They are part of the Eastern Arc Mountains and have a lot of biodiversity and a lot of species that live only there. The Udzungwa Mountains National Park is in these mountains, and it's home to several endemic primates and bird species.
Mount Rungwe is 2,981 meters or 9,780 feet. It's a dormant volcanic mountain in the Southern Highlands, with lush rainforest and grasslands high up. Several plants and animals there are endemic.
The Mafinga Hills go up to 2,320 meters or 7,612 feet. It's the highest point in the Southern Highlands. Rugged terrain, a lot of biodiversity, and plants and animals that are special to the area, some of them endemic.
Mount Guruguru is about 2,000 meters or 6,562 feet. Not many people know it, but it has a lot of geological history. It's part of the Rift Valley escarpment and has unusual rock formations, so it's interesting for geologists.