EDITED ANSWER PER DAVID'S RESPONSE:
Here's a kind of hackish way. I'm guessing there's an easier way. But you could suppress the bar labels and the plot text of the labels by saving the bar positions from barplot
and do a little tweaking up and down. Here's an example with the mtcars data set:
x <- barplot(table(mtcars$cyl), xaxt="n")
labs <- paste(names(table(mtcars$cyl)), "cylinders")
text(cex=1, x=x-.25, y=-1.25, labs, xpd=TRUE, srt=45)