Best Bets on TV Tonight

Hip-hop mogul Sean "P. Diddy" Combs speaks to young adults about the issues and the importance of casting their vote on "Speak Now Special" (8 p.m., BET).
Three U.S. presidents and their crucial decisions are examined in "Decisions That Shook the World" (8 p.m., Discovery), a special hosted by presidential historian Michael Beschloss and narrated by actor Morgan Freeman. First, the spotlight is on Lyndon B. Johnson and civil rights. On Oct. 19, the focus will be Ronald Reagan and the Cold War; and Oct. 26, Franklin D. Roosevelt and World War II.
The case of "Typhoid Mary" (8 p.m., PBS), a cook who became a symbol of a public health menace in New York in the early 1900s, is revisited in a dramatization called "The Most Dangerous Woman in America." Mary Mallon (portrayed by Marian Tomas Griffin) was a "healthy carrier" of typhoid fever who was quarantined against her will.
Vivica A. Fox and Mos Def host the two-hour special honoring the pioneers and hot new artists of the genre, Hip Hop Honors (9 p.m., VH1). Salt-n-Pepa, Doug E. Fresh, Public Enemy, Nas, Beastie Boys and Sugarhill Gang are among the honorees.
"The Club" (10 p.m., Spike TV) shows the inner workings of a hot nightclub in Las Vegas, from the frustrations of the owner to the DJ spinning the tunes.