Boo was resurected by Babi Di. Althogh many people spell it Buu, the English translation on the Japaneese toy is Boo. He can turn people into food and eat them which I fond kinda cool. The only way to destroy Boo is to completely vaporize him as he can regenerate his limbs with ease and pull himslef back together without having to waste any energy doing so. Majin Boo was also the first Dragon Ball enemy to actually detsroy the Earth. His forms in the show are as follows (Every form can be called Majin Boo, and these are not official names, but the most common ones that make sense) Click here For a list of Boo's forms.
Many thanks GogetaMega for the Boo Information.

Bulma is one of the first characters introduced in the Dragonball series. She actually runs into Goku on her motorcycle. She is trying to search for the Dragonballs as well as Goku so they team up, and they become good friends and venture everywhere together throughout the whole series of Dragonball. As she gets older, she becomes a scientist, like her father, and the owner of the Capsule Corporation. Bulma can build almost anything, including a time machine. She eventually has two children with Vegeta, they are Trunks and Bra.

Burter is one of the members of the Ginyu force, and somewhat powerful. He is known for his speed, but is usually teaming up with Jeice for his attacks. He is usually successful, even without Jeice, until he meets Goku for the first time.

Cell is an android made up of cells of mostly Piccolo, Goku, Freeza collected by a spy robot made by Dr. Gero. He came from the futer and extremely evil.

Coola is Freeza's brother, and makes two appearances in movies 5 and 6. In movie 5, he goes to Earth to seek revenge on Goku for killing his brother. In movie 6 he is reformed as Metal Coola after being blasted into a star by Goku, by the Big Ghetti Star. The Ghetti star was formed by a computer chip floating around in space by using raw material around it. After Coola was re-formed, he was then the controller of it, and possessed extreme power.

In the earlier episodes of DBZ, he was the most powerful preson in the universe. He controlled Vegeta, Nappa, and Radditz, and pretty much the whole galaxy. He has a pricate army called the Ginyu force, which has never failed him (Untill they meet Goku ^_^) And when Goku challenges him, it is the biggest turning point in DBZ.