Another Bob Dylan one, which I am amazed didn’t come up yet: he’s in “Mr. Jones” by Counting Crows.
Another Ronald Reagan one (sort of): “Bonzo Goes to Bitburg” by the Ramones, criticizing his visit to a cemetery that contained some graves of SS officers. The song was difficult for them to do, because they had been big Reagan supporters until then.
Some artists that have already been mentioned:
Mojo Nixon also recorded “Don Henley Must Die!”. Supposedly he later changed it to “Michael Bolton…” when performing it live.
In addition to “Vincent”, Simon and Garfunkel also recorded a song called “So Long, Frank Lloyd Wright”. I think it is on the album “Bridge Over Troubled Water”.
Also:
Dexy’s Midnight Runners mention Johnny Ray in the first line of “Come on, Eileen”
Bruce Springsteen, “Thunder Road”: “…Roy Orbison singing for the lonely…”
The Smithereens, “Behind the Wall of Sleep” mentions Jeannie Shripton (a fashion model, I think) and Bill Wyman.
Rolling Stones, “You Can’t Always Get what you Want” mentions Mr. Jimmy, which I believe refers to Jimi Hendrix.
Now, a few where the person’s name isn’t mentioned, but the song is about them:
George Harrison wrote “All Those Years Ago” in honor of John Lennon. For that matter, I think one of Lennon’s early solo song was a condemnation of Paul McCartney, but I don’t remember the title.
U2’s “Angel of Harlem” about Billie Holliday.
Carly Simon’s “You’re so Vain”: supposedly about her relationship with Warren Beatty, but I don’t know if she has said this, or just other people have.
Don McLean’s “American Pie” is loaded with what appear to be references to Buddy Holly, the Big Bopper, Richie Valens, Bob Dylan (again!), the Beatles, the Byrds, the Rolling Stones, James Dean…but I don’t think he has admitted to any of them. I know the lyrics have been dissected on this board.