Jessica has been reading through The Poisonwood Bible, which touches upon Patrice Lumumba and the Congo Crisis at the end, so I tracked down these Wikipedia articles on the Congo and Leopold II and Congolese independence for her:
Leopold II of Belgium: 1835-1909, son of Leopold I of Belgium, who married Princess Charlotte and arranged then-Princess Victoria's marriage to Prince Albert.
Congo Free State: Leopold II's private state in the Congo, 1885-1908; now the Democratic Republic of the Congo.
King Leopold's Soliloquy: 1905 satirical pamphlet by Mark Twain criticizing Leopold II's actions in the Congo, in which the King supposedly argues that bringing Christianity to the country outweighs a little starvation (text available from American Museum of Natural History).
Force Publique: private army used by Leopold II to govern the Congo Free State and enforce production quotas; evolved into local colonial army after Belgian takeover of the Congo in 1908; nationalized and Africanized by Patrice Lumumba in 1960, deeply involved in the Congo Crisis, which led to Joseph Mobutu seizing power in 1965; Mobuto's overthrow led to the First Congo War from 1996-1997 and the resulting tensions then led to the Second Congo War from 1998-2003.
King Leopold's Ghost: book published in 1999 (made into a documentary in 2006) which details the history of the Congo Free State, and mentions the roles played by George Washington Williams, who coined the term "crimes against humanity", William Henry Sheppard, E. D. Morel, Sir Roger Casement and Joseph Conrad in reporting, documenting and publicizing the atrocities carried out by Leopold II in the Congo.