Revolutionary Memory is most likely a moniker discarded by whoever was responsible for the indicdent.  It is unlikely that any future attacks will be attributed to the group.

Revolutionary Movement of October 8 (MR-8)

After the collapse of the military regime in 1985, the MR-8 was reorganized within the Party of the Brazilian Democratic Movement, (Partido de Movimento Democratico Brasileiro), a centrist political party. As a political organization, the MR-8 remains active and produces a newsletter, Hora do Povo. The group has not been responsible for any recent attacks. As a terrorist organization, the MR-8 is not considered active.

Fighters for Freedom -- Rival
Popular Revolutionary Action -- Ally (Suspected)
Revolutionary People's Struggle -- Founding Group

Experts believe that Revolutionary Nuclei is the primary successor of one of Greece's most infamous terrorist organizations, the now defunct Revolutionary People's Struggle (ELA).  Revolutionary Nuclei's communiques share the anti-capitalist, anti-imperialist, anti-American tone of ELA's public statements.  During 1999 and 2000, Revolutionary Nuclei was extremely active.  The group claimed responsibility for at least 14 bombings during that period.  Their targets have included Greek government buildings, the offices of American companies, and banks.  Revolutionary Nuclei's most damaging attack was the April 1997 bombing of the Intercontinental Hotel.  The attack, which took place a few days before the hotel was to host an international economic conference, was in protest of the NATO bombing campaign against Yugoslavia.  Virginia Konstantinou, an employee of the Altec Information Systems Company, was killed.  Arson attacks and terrorist bombings are extremely common in Greece, but they very rarely kill people, so the Intercontinental Hotel attack distinguishes Revolutionary Nuclei from most other Greek terrorist groups.

Revolutionary Nuclei seems to have been inactive since November 2000, the end of an intense two-year bombing campaign.  At least twice since then, a group claiming to be Revolutionary Nuclei has claimed responsibility for an attack, but these bombings involved low-technology weapons such as Molotov cocktails, whereas Revolutionary Nuclei typically used more advanced weapons such as time bombs.  Greek police doubt that any of the recent attacks which have been claimed by Revolutionary Nuclei were actually the work of that group.  On the other hand, in July 2003 a bomb was planted at the insurance company Alico that bore a suspiciously strong resemblance to the bombs planted by Revolutionary Nuclei, according to Greek counter-terrorism officials.