Demonstrators hope their continued gatherings will put pressure on military leaders to keep their promises of reform.
The groups that sparked the 18-day uprising leading to Mubarak's downfall called the massive gathering the "Friday of Victory and Continuation," a name reflecting both their pride in forcing a national leadership change and their worries about the future.
Protest leaders addressed the sprawling crowd, saying demonstrations and rallies need to continue until the military does more to dismantle Mubarak's regime, which still holds considerable power even after his ousting.
Protesters want the army to dissolve the caretaker government headed by Prime Minister Ahmed Shafiq, which was appointed by Mubarak in his final weeks and contains many of his stalwarts.
Also, they are calling for the lifting of emergency laws that give police near unlimited powers of arrest. So far, the military has not moved on either issue, or on another demand for the release of thousands of political prisoners.
But far from cracking down, the army's attitude toward Friday's rally could mark a different strategy: Turn the "revolution" into a nationalist event, celebrate it, but then move on.
Friday's rally appeared to far surpass the quarter-million people who packed the largest of the anti-Mubarak demonstrations of the past month.
In other countries across the Mideast and Africa, though, unrest is growing.
Yemen, Bahrain and Libya have seen deadly clashes this week between protestors and authorities.
The Associated Press contributed to this report.