Imus' history of comments is well-documented and not only on his show. Things I know I heard, some are his some are from people on his show.
His referring to black journalist Gwen Ifill as a "cleaning lady" on a few occasions.
The term "sand monkeys" got thrown around a lot during stories about Middle East, especially when Saddam Hussein or Yassar Arafat came up.
Bernard (as the Cardinal) turning the song "My Wild Irish Rose" into "My Wild Irish Ho's" with a line that would get bleeped when MSNBC would replay it, yet they did often replay it. Some have mentioned elsewhere that Imus' friend and newsreader Charles McCord was an innocent victim of the firing, McCord often co-wrote many of the comedy bits on the show. When a Cardinal routine was flopping or going badly, Bernard would turn on McCord (jokingly). There was also a running joke for a while of the Cardinal asking McCord if he had seen the movie Amistad, and calling him a racist when he said no, usually asking would he like it better if it had ended like Titanic.
"The Cardinal" would end most appearances with a question "Which Doesn't Belong and Why?" He would usually name two figures in the news and Imus. The correct answer was usually not obvious and the explanations often involved racist or homophobic digs at Imus and the other names. If say Oprah was the correct answer, the reason usually involved saying that she "had never slept with a black man" and that Imus had.
Sid Rosenberg, a one time sports reporter on the show, got in serious trouble for comments he made about the Williams sisters. He also got the wrong shirts back from the dry cleaners after 9/11, which he refused to return and wore frequently, it turned into a recurring joke that he was wearing the unclaimed clothes of someone who may have died in the terrorist attack on the WTC.
Imus would often call Jewish coworkers on the phone on Jewish holidays when they weren't supposed to do work, including answer the phone except in emergencies. He would then lambast them for not keeping to their faith.
The New York Knicks, and especially Patrick Ewing, were frequent targets of abuse. "Knuckledraggers" and
'pimps" were often used, but this was frequently to get the goat of he radio station which carried Knicks games and their then sports reporter who was a play by play man for Knicks broadcasts. They also accused him of sleeping with Ewing on a regular basis. This reporter (Mike Breen) often took part in some antics himself.
On rare occasions when Imus took calls (usually for contests), the callers (screened by McGuirk) often sounded like lower class or uneducated Southerners. Mobile home jokes and accusations of being drunk in the early hours of the morning usually followed.
Imus used to explain his job as a DJ from his music playing days decades before as, "Talking dirty to women on the air and playing the hits."