All were convicted of assisting in a plot led by Dhiren Barot, who was sentenced to life in prison last year.
"Barot was the instigator of this terrorist planning," said Justice Neil Butterfield, presiding in Woolwich Crown Court. "Each one of you was recruited by Barot and assisted him at his request."
Barot, 35, a British convert to Islam, was convicted of planning to use vehicles packed with explosives to attack such targets as the International Monetary Fund in Washington and the New York Stock Exchange and Citigroup headquarters in New York as well as London hotels and train stations.
Prosecutors also charged that Barot also had drawn up plans to build and detonate a so-called dirty bomb, which combines radioactive materials with conventional explosives.
Speaking for the crown, Johnathan Laidlaw said the defendants gave Barot the help he needed to operate. "They were his support team."
While Barot planned the attacks, Laidlaw said he needed the help with false identities, access to false bank accounts and research materials as well as minders and drivers.
British Home Secretary John Reid said their goal was "mass murder, mass panic and utter devastation." In his comments on the case, he said it "showed the extent of the very real and serious threat the UK faces from terrorism".
Sentenced were: Abdul Aziz Jalil, 26 years; Junade Feroze, 22 years; Mohammed Naveed Bhatti and Nadeem Tarmohamed, 20 years each; Zia ul Haq, 18 years; Omar Abdur Rehman, and Qaisar Shaffi, 15 years each.
Shaffi was convicted of conspiracy to murder after a month long trial that ended earlier this week. The other six pleaded guilty in April to conspiracy to cause explosions likely to endanger life.
The judge told the defendants the suffering their families would experience with their incarceration "is but a tiny fraction of the suffering that would have been experienced had your plans been translated into reality."
Barot's sentence was reduced from 40 years to 30 years last month as a court ruled that the plot had not progressed far enough to merit the stiffer punishment.
He was described by Britain's top anti-terrorist detective as "a long-term, dedicated, committed member of al Qaeda."