First, the basic facts: Agrippina Minor was born in 16 AD. She was the great-great grandniece of Julius Caesar, the great-granddaughter of Caesar Augustus, the granddaughter of Agrippa (Augustus' General) and Julia (Augustus' daughter), and the daughter of Germanicus and Agrippina the Elder. She was the sister of Caligula, the niece and wife of Claudius, and the mother of Nero.
Agrippina Minor was first married to Lucius Domitius Ahenobarbus, but he died when their son, Nero, was only three years old. In 39 AD, Agrippina was exiled by her brother, Caligula, for plotting against him along with her sister Livilla. The Praetorian Guard eventually killed Caligula and acclaimed Agrippina's uncle, Claudius, as Emperor. At the time, Claudius was married to a sexual predator named Messalina, but Claudius eventually had her executed because of her blatant public misbehavior. Claudius' advisors, led by Pallas, an influential member of his staff, convinced him to marry again. This time the candidate was Agrippina Minor, who had returned from exile but had not been pardoned. She was rumored to be involved with Pallas.
Claudius revoked Agrippina Minor's exile and took her as his forth wife in 49 AD. Claudius was 58 years old. One of Agrippina's clear goals from the beginning was to ease the way for her son Lucius Domitius Ahenobarbus (Nero) to succeed Claudius ahead of his own son Britannicus. Claudius officially adopted Nero in 50 AD, and that is when Agrippina's son took Claudius' family name and became Nero. In 51 AD, Nero was raised above Britannicus to the rank of Princeps Iuventutis (Leader of Youth). This elevation of Nero clearly marked him as the heir to the throne, and his portrait began to appear on Roman coinage along with issues of Agrippina. Why Claudius allowed Nero to be elevated above Britannicus is still a mystery, but, given the behavior of Messalina, it may have been because he believed Britannicus might not really be his son. Nero's path to power was sealed by his marriage to Claudius' daughter Octavia. All that remained was the death of Claudius.
And here is one of the most hotly disputed points about Agrippina Minor: did she poison Claudius? Obviously, after almost 2000 years, the evidentiary trail is cold. But even at the time -- and more importantly, even after she was dead and gone at the hands of Nero -- no one brought forward any real evidence to back up the allegation that she was a poisoner. Three circumstances make the poisoning charge unlikely: first, as the wife of Claudius, she was already at the summit of power and had nothing to gain by taking the risk of rushing his exit -- on the contrary, the longer he lived, the greater her power grew; second, she had already ensured Nero's succession and had reasonable hopes of retaining her influence when he would become Emperor; and, third, Claudius was already clearly on his last legs due to acute alcohol poisoning. Most legitimate historians now believe that Agrippina had no reason to insinuate the alleged infamous plate of poison mushrooms.
With Claudius dead, Nero became Emperor, and Agrippina ruled both Nero and the state. And here is the second unsubstantiated charge against Agrippina. Nero's and her own senatorial enemies, as well as writers in the pay of the later Flavian dynasty of Emperors, claimed that Agrippina had a sexual affair with Nero in order to strengthen her maternal control over him. Although this story was repeated well into the 20th century, many modern historians, especially "feminists", point out that such allegations were predictable reactions of contemporary male rivals, who were obviously jealous of her influence, and that similar charges were leveled against any Roman women who achieved power.
Judgement of the veracity of the various allegations of Agrippina wrongdoing is complicated by the fact that she, herself, orchestrated her image as a totally ruthless adversary, willing to do anything to keep first Claudius and then Nero in power. This was an obvious attempt to dissuade potential and real enemies.
What is clear is that Agrippina totally dominated the end of Claudius' reign and controlled Nero and his palace during Nero's early years as emperor. But by 59 AD, Nero decided he could no longer tolerate his mother's interference and plotted to have her killed. Knowing that Agrippina would be alert to any attempt to poison her, Nero set up an elaborate plot in which Agrippina was invited on a sea voyage with Nero. After she boarded and while she was waiting for Nero's barge to meet her at sea, the specially built self-destructing ship collapsed around her. Agrippina managed to escape from the "accident" and swim back to shore. Nero abandoned pretence and ordered his soldiers to kill his mother. Nine years later, after numerous outrageous adventures, Nero, himself was hounded to his suicide by the mob.
Agrippina appears to have been just as ambitious and ruthless as the men who surrounded her, but she was easily twice as effective. Hardly anybody thinks that she was an archetype for Roman matronly respectability. It is certain, however, is that she brought some order into the Palace of Claudius, and that, unlike the descents into terror of some other Emperors, the reign of Claudius steadily improved as alcohol progressively numbed his faculties and as Agrippina's power increased correspondingly. Specifically, she ended the long string of Senatorial executions that Messalina had instigated.
It is also obvious that young Nero, under her influence, was fairly reasonable and efficient, and that removing her was an early sign of his spiral into the realm of madness and debauchery.
The best account of Agrippina's life and role in the declining years of the Julio-Claudian dynasty (which started with Julius Caesar and ended with Nero) is not on the Internet but in a hard copy book by Anthony A. Barrett called Agrippina, Sex, Power and Politics in the Early Empire. Be warned, however, that this is not the light read that its beguiling title might suggest -- it has 250 pages of fine-print text, 50 pages of footnotes, and a 20-page bibliography. It is available in paperback from online booksellers and in a few better bookstores in Rome.
http://www.britannica.com/bcom/eb/article/0/0,5716,4140+1+4090,00.html Britannica.com, with links to Claudius and Nero articles, and
http://myron.sjsu.edu/romeweb/ladycont/art4.htm with a link to a list of bios of other Roman women at http://myron.sjsu.edu/romeweb/ladycont/ladycont.htm, and
http://www.peicommerce.com/HISTORY/ROMAN/AGRIPNA2/AGRIPNA2.HTM A monetary history with examples of Agrippina coins, and
Extensive, but in German.
The Annals of Tacitus (books XI through XVI) give a great deal of gossipy information on court life during Agrippina's run in the Palace: http://classics.mit.edu/Tacitus/annals.html
An extensive explanatory review of the Barrett book from the Bryn Mawr Classical Review is at: http://ccat.sas.upenn.edu/bmcr/1997/97.03.11.html.
A very good recording of Handel's opera Agrippina is available on three CD's at the rather steep price of $50 at Amazon.com: http://www.amazon.com/exec/obidos/ASIN/B0000041JV/qid=966773374/sr=1-5/104-0434494-3350327.
An account of the 1999 rediscovery
of Agrippina's villa on Rome's Janiculum Hill during construction of the
Vatican's "Jubilee 2000 parking lot" is at http://www.bib-arch.org/aomj00/fn.html#villa.