There's a detailed article from November 2001 here:

When [9/11 hijackers] Hanjour and Almihdhar showed up at DMV Express [in Virginia], they apparently already had two forms of ID--a passport and a legal visa would have been accepted---because they did not submit DL6s to establish their identity. But they did submit DL51s, to "prove" their Virginia residence. Martinez [an illegal alien day laborer from El Salvador who they'd hired to help them get driver's licenses] allegedly certified the forms for both of them.

On the forms, the men claimed to live in an apartment complex on the 5900 block of Leesburg Pike--one block down from the strip mall. "This address did not belong to either Hanjour or Almihdhar," [FBI agent] Gomez wrote in his affidavit, "but was rather the address that appeared on Martinez's Virginia identification card. Martinez no longer lived at the address, but had in the past."

With their newly minted photo IDs, the two suspected terrorists drove back with Martinez to Culmore. "At the 7-Eleven they all got out of the van," wrote Gomez. "Hanjour and Almihdhar went inside the store and appeared to use the ATM machine. They then came out, paid Martinez $100 in cash for his efforts, and left in the van. Martinez did not see them again."

But the Virginia DMV had not seen the last of these two. Hanjour and Almihdhar were now qualified to certify the legal residency of other terrorists.

That is exactly what they did the next day--at a DMV about three miles from the Pentagon on South Four Mile Run in Arlington.

Wrote Special Agent Gomez: "DMV records also show that Hanjour and Almihdhar used the address Martinez gave them on August 1, 2001, to complete DL51 forms for [9/11 hijackers] Majed Moqed (Moqed) and Salem Alhazmi (Alhazmi) on August 2, 2001..."

Three other suspected hijackers showed up at the Arlington DMV that very same day. They, too, needed witnesses to help them secure Virginia IDs. But unlike Hanjour and Almihdhar, they needed not only DL51s, to establish a residence, but also DL6s, to establish their identities. That meant they had to have the help of a witness, a notary, and a lawyer...

...Herbert and Lopez-Flores [also illegal alien day laborers] got into Herbert's car and drove to an attorney's office on Columbia Pike in Falls Church. The three Arab men followed in their van...

One of the Arab men in the office that day was Ahmed Alghamdi, one of the suspected hijackers of United Airlines Flight 175, which flew into the World Trade Center towers. Lopez-Flores vouched for his DL51 form, on which Alghamdi falsely claimed to live on Edison Street in Alexandria.

Abdul Alomari was another one of the Arab men in the law office that day. He is a suspected hijacker of American Airlines Flight 11, which also crashed into the World Trade Center towers. Alomari claimed to live on Buchanan Street in Arlington. "Oscar Armando Diaz," whom the FBI believes to be Villalobos, certified Alomari's residency on the DL51. (The actual resident at this location was Villalobos' cousin.)

Villalobos, who told the FBI he believed the men to be Pakistani or Iraqi, added an interesting note. "Villalobos said the attorney then came out of his office and signed the forms as well," wrote Special Agent Weidner. "Here, Villalobos noted that the attorney conversed with the 'Pakistanis' in 'their language.' After this conversation, each 'Pakistani' man paid the secretary $35, and then all returned to the Arlington DMV office. Once back at the DMV office, the 'Pakistani' men paid Villalobos $50 for his assistance and then went into the DMV to get identification cards."

When the FBI later showed Villalobos photos of the suspected September 11 hijackers, he identified five of them--Hani Hanjour, Salem Alhazmi, Majed Moqed, Khalid Alghamdi and Abdul Alomari--as being at the Arlington DMV that day. "These identifications," Special Agent Weidner wrote, "were later confirmed by Virginia DMV records which show that all five men did in fact conduct various transactions relating to Virginia identifications cards at the Arlington DMV on August 2, 2001..."

Much more information at the link.