How does your sect differ from the other branches within the major religion?

Here's a comparision chart of Shia's and Sunnis:
http://www.religionfacts.com/islam/comparison_charts/islamic_sects.htm

How and where did this particular branch develop?

According to Encyclopedia Britannica and others, the Shia are believed to have started as a political party and developed into a religious movement, influencing Sunnis and producing a number of important sects.

- This was early in the history of Islam.

- Disagreement broke out over who would succeed Muhammad as leader of the Muslim community. While the Sunnis followed the companions of Muhammad, the Shia followed Ali.

- According to various Islamic people, this division officially took place in The First Fitna, or civil war sometime in the late 7th century A.D.

How does this monotheistic religion differ from the other two major monotheistic religions?

Christianity:
From the Greek:christos, 'Anointed' - referring to Jesus Christ।
Founder: Jesus Christ(c. 4 B.C. - 30 A.D.)
Three main groups: Orthodox, Protestant and Roman Catholic।
2,200 Million(2.2 Billion) followers

Islam:
Derived from an Arabic word for 'submission'. Also related to the Arabic word salaam, 'peace'.
Founder: Mohammed(570 - 632 A.D.)
Two main groups: Sunni and Shia
1,500 Million(1.5 Billion) followers

Judaism:
From the Hebrew:Yehudim, 'Judah'.
Abraham (First Patriarch, born c. 1800 B.C.)
Several divisions, including Hasidic, Conservative and Reform Judaism. Ethnic groupings include Ashkenazi (The majority) and Sephardi Jews.
14 Million followers

What traditions or rituals do they follow?

1. Eid al-Adha, which marks the end of the Hajj or pilgrimage to Mecca.

2. Eid al-Ghadeer, which is the anniversary of the Ghadir Khum, the occasion when Muhammad announced Ali's Imamate before a multitude of Muslims.

3. Arba'een commemorates the suffering of the women and children of Hussein ibn Ali's household. After Hussein was killed, they were marched over the desert, from Karbala (central Iraq) to Shaam (Damascus, Syria).

What are the demographics of where this sect can be found? How many people practice this?

It is variously estimated that 10–20% of the world's Muslims are Shia, while the remaining larger percentage follow Sunni Islam. This puts them somewhere between 165-to-190 million people.

The Shia majority countries are Iran, Iraq, Azerbaijan, and Bahrain; all are coloured in red.

What holy book do they use and what holy days do they observe?

Like other schools of thought in Islam, Shia Islam is based on the teachings of the Islamic holy book, the Quran and the message of the final prophet, Muhammad. Some holy days observed are...
1. Eid-ul-Fitr, often abbreviated to Eid, is a Muslim holiday that marks the end of Ramadan, the Islamic holy month of fasting.

2. The Day of Ashura is commemorated by Shi'a Muslims as a day of mourning for the martyrdom of Husayn ibn Ali, the grandson of Muhammad at the Battle of Karbala on 10 Muharram in the year 61 AH (October 10, 680 AD).

http://www.youtube.com/watch?v=tKDAUGq-a8s

What is the place of worship? What are the major features of this place?

As all Muslims do, Shia's pray in Mosques. The Imam Hussein Shrine in Karbala, Iraq is a holy site for Shia muslims.

-It is one of the oldest mosques in the world.

-It stands on the site of the grave of Husayn ibn ‘Alī, the second grandson of Muhammad, near the place where he was killed during the Battle of Karbalā in 680 C.E.

-The grave of Husayn is enclosed within a cage-like structure, found directly beneath the golden dome. Al Abbas Mosque is located nearby.

-The boundary wall of the shrine surrounds wooden gates covered with glass decorations. The gates open into a courtyard separated into smaller rooms or precincts with many "Iwans" along the walls.

Map of Shi'ite minority