The eight men - who are members of the Jumatul Mujahedeen Bangladesh group - were convicted of being involved in a bombing campaign which mainly targeted police, court and government buildings.
Jumatul Mujahedeen Bangladesh wants to replace the country's secular legal system with Islamic law.
More than 430 small homemade bombs exploded within an hour of each other across Bangladesh on August 17, 2005. Two people were killed and at least 125 injured in the blasts.
Leaflets from the banned group were found at the bomb sites.
The group's leaders confessed to ordering the bombings to draw attention to their cause.
The defendants were also charged with a bomb attack at the court in October last year that killed one person.
While coming out of the court the defendants sang Islamic songs, the United News of Bangladesh agency reported.
In May, a court sentenced seven other Islamists to death, including the group's two top leaders - Sheikh Abdur Rahman and Siddiqul Islam - for their involvement in the killing of two judges in a bombing on November 14.