Caligula - Emperor Julio-Claudian
Page on Caligula from an annotated gallery of the first 12 emperors of ancient Rome.
Caligula - Paper on Caligula, by Jay Key
History has not been kind to Caligula, and for good reason, due to the lasting volumes of maniacal and savage anecdotes depicting a mad ruler. However, during his first year in office, Caligula was effective and somewhat politically capable to be ruler of the world, and his vicious maneuvers were a necessary part of his political agenda -- to return Rome to Caesar's form of rule.
Chronology by Barbara F. McManus who says Caligula's "behavior demonstrates what can happen when absolute power is combined with a total lack of responsibility and respect for others."
Gaius Caligula of Rome
Article on the madness of Caligula, schizophrenia, which got worse after his illness in A.D. 37.
Crazy Caesars of Rome
Madness among royals frequently comes from inbreeding, but that wasn't the case with the Julio-Claudians. Caligula had epilepsy and appears to have suffered from post-encephalitic schizophrenia.
From your Guide, the names and dates of rule of the emperors from Augustus in 27 B.C. to Numerian (285 A.D.).
An Online Encyclopedia of Roman Emperors
Articles on Julio-Claudian and Flavian emperors with timeline for emperors through Constantine XI (XIII) Palaeologus.
Stemmata of the Julio-Claudian emperors
The lines of consanguinity among the first five emperors are hard to keep straight. Even with this chart, it will take time to unravel the bloodline, marriage and adoption threads, but it's a useful reference tool.