NRO has a good compilation of information about the two brothers suspected (for very good reason) of setting off the explosives in Boston. As Scott noted, they apparently are of Chechen origin. And apparently they are Muslims.
Tamerlan Tsarnaev, now dead, is quoted in a photo essay as saying that he doesn’t drink or smoke anymore because “God said no alcohol.” He also complained that “there are no values anymore,” and worries that “people can’t control themselves.”
Buzzfeed reports that Tamerlan had a YouTube page focused on Islam. Reportedly, the most recent subscription is to a channel called Allah is the One. He also created four playlists, one called Islam, and another called Terrorists, which has two deleted videos.
Adam Serwer says that Tamerlan had a YouTube page where he posted religious videos, including a video of Feiz Mohammad, a fundamentalist Australian Muslim preacher who rails against the evils of Harry Potter. One video is dedicated to the prophecy of the Black Banners of Khurasan, which is embraced by Islamic extremists, particularly Al Qaeda.
The prophecy states that an invincible army will come from the region of “Khurasan,” a large portion of territory in central Asia. Aaron Zelin, a fellow at the Washington Institute for Near East Policy, says that this prophecy is important in Al Qaeda’s ideology. Based on the prophecy, some jihadists believe that Khurasan — a historical region spanning northeastern and eastern Iran and parts of Turkmenistan, Uzbekistan, Tajikistan, Afghanistan, and northwestern Pakistan — is the region from which they will inflict a major defeat against their enemies in the Islamic version of Armageddon.
UPDATE: The other terrorist, Dzhokhar Tsarnaev (Tamerlan’s brother) reportedly has posted links to videos suggesting solidarity with Islamic forces fighting in Syrian. He also linked to cites with such titles as “Salamworld, my religion is Islam” and “There is no God but Allah, let that ring out in our hearts”.