Committees of the U.S. Congress - When you click on a committee, it will show you the committee activity. If you want to look up the membership, there is a spot towards the upper right side of the page with a link to COMMITTEE MEMBERSHIP. Click on that and you can see all the members as well as the Chairman and the Ranking Member of the committee. This can be helpful when decided who else you might contact on a particular issue.
Homeland Security - Committees & Departments - contact info for both the House and Senate committees chairmen and ranking members and Executive department heads.
Armed Services - Committees and Departments - contact info for both the House and Senate committees chairmen and ranking members and Executive department heads.
US Senate Committee Assignments of the 119th Congress - this lists each senator and then shows all the committees that senator serves on
US Senate Committees - lists and provides links for all the committees and subcommittees for the Senate.
Government Sources by Subject: [U.S. Executive Branch] Departments and Agencies - lists and provides links for all the major departments of the executive branch as well as many of the bureaus under them.