Here is a timeline from ThinkProgress.org. As a side note, it corresponds to the timelines presented in today's NYT and W. Post:
2003 Rep. Mark Foley (R-FL) has sexually explicit IM exchanges with an underage boy who worked as a Congressional page. [ABC News, 9/29/06]
2005 Rep. Mark Foley (R-FL) sends inappropriate emails to another former Congressional page. [CREW]
SEPTEMBER 2005 Rep. Rodney Alexander (R-LA), who sponsored the page, learns of the e-mails from a reporter. [AP, 9/29/06; CQ, 9/30/06]
FALL 2005 Tim Kennedy, a staff assistant in the [Speaker J. Denis Hasterts] Office, received a telephone call from Congressman Rodney Alexanders Chief of Staff who indicated that he had an email exchange between Congressman Foley and a former House page
[Mike] Stokke [Deputy Chief of Staff for Speaker Hastert] called the Clerk and asked him to come to the Speakers Office so that he could put him together with Congressman Alexanders Chief of Staff. [Hastert Statement, 9/30/06]
LATE 2005 Rep. John Shimkus (R-IL), Chairman of the House Page Board, was notified by the then Clerk of the House, who manages the Page Program, that he had been told by Congressman Rodney Alexander (R-LA) about an email exchange between Congressman Foley and a former House Page. Shimkus interviewed Foley and told him to cease all contact with this former house page. He did not inform Rep. Dale Kildee (D-MI), the only Democrat on the House page Board. [Roll Call, 9/29/06]
FEBRUARY/MARCH 2006 Alexander tells NRCC chairman Tom Reynolds about the existence of e-mails between Mark Foley and a former page of Mr. Alexanders. Reynolds tells Speaker J. Dennis Hastert (R-IL) about the emails and his conversation with Alexander. [Reynolds Statement, 9/30/06; Roll Call, 9/30/06; Hastert Statement, 9/30/06]
SPRING 2006 House Majority Leader John A. Boehner (R-Ohio) learns of inappropriate contact between Foley and a 16-year-old page. After leaning about Foleys conduct, Boehner told Speaker of the House J. Denis Hastert who assured Boehner he would take care of it. Later, Boehner changed his story and told the Washington Post he didnt remember whether he talked to Hastert. [Washington Post, 9/30/06; New York Times, 10/1/06]
JULY 27, 2006 Foley, still co-chairman of the Congressional Missing and Exploited Childrens Caucus, attends a signing ceremony at the White House for the Adam Walsh Child Protection and Safety Act of 2006. [White House, 9/27/06; Talkingpointsmemo, 9/30/06; Washington Post, 10/1/06]
SEPTEMBER 28, 2006 ABC publishes emails between Foley and former page. [ABC, 9/28/06]
SEPTEMBER 29, 2006 Foley resigns. [ABC, 9/29/06]
SEPTEMBER 29, 2006 ABC publishes sexually explict Instant Messages between Foley and several former pages. [ABC, 9/29/06]
SEPTEMBER 29, 2006 Aides to the speaker [Hastert] say he was not aware until last week of inappropriate behavior by Rep. Mark Foley, R-Fla., who resigned on Friday after portions of racy e-mail exchanges between him and current and former underage congressional pages became public. [Chicago Tribune, 9/30/06]
SEPTEMBER 30, 2006 Hastert admits he was told about the emails by Reynolds in the spring. [Hastert Statement, 9/30/06]