All kinds of federal office holders can be impeached. The President is the most well known, but judges are the most common.
The Senate
The Senate tries federal office holders who have been impeached by the House.
Judges
As of mid-2009, seventeen US federal office holders have been impeached, including presidents Andrew Johnson and Bill Clinton. One cabinet member has been impeached, one senator, and one US Supreme Justice. Twelve other federal court justices have been impeached. Note that impeachment does not mean being removed from office. It merely means that Congress brings charges against the office holder. (See link below.)
All government officials can be impeached and its the safeguard against corruption at the federal level. The president can be impeached as well as any other holder of public office.
The President could be impeached and removed from office after an impeachment trial. After he was removed from office, he could then be prosecuted like any other person.
Clinton was impeached but not officially removed from office, and Nixon was to be impeached but resigned before he could be impeached.
President Andrew Johnson was impeached when he violated the Tenure of Office Act. The Tenure of Office Act was repealed in 1887.
All government officials can be impeached and its the safeguard against corruption at the federal level. The president can be impeached as well as any other holder of public office.
Andrew Johnson became the first president to be impeached in 1868 for violating the Tenure of Office Act (among other things). He was acquitted by a single vote. (Bill Clinton was the only other President to be impeached. He was acquitted as well.
The spoils system is the partisan replacement of office holders.
Impeached