As the Iraq war ends, I'm still bitter about my cohorts who should have served in Vietnam, but didn't, many of them prominent Republicans. At the top of the list are George W. Bush and Dick Cheney, as well as Bill Clinton. Al Gore is the only one to have served in the military in Vietnam. But also Mitch McConnell and John Boehner both avoided service, although Boehner may be young enough that we was not under the draft. He still could have served if he had wanted to.
I'm not sure where this web page showing who served came from, but it seems pretty accurate, although it is now somewhat dated.