The irony of perspective
Because each person's point of view is subjective and limited, it's seriously tempting to slide into the feeling of correctness, but without all the evidence, who could be sure? Rorty observes the irony between our beliefs and reality, because we often wrongly believe that they are the same thing.
The irony of humor
This book literally has "irony" in its title, and he calls chapter two "Ironism and Theory" so the book treats irony very directly. The main use of irony in Rorty's argument is that we should regard our beliefs about ourselves with a sense of humor or detachment, because it's easy to believe that we're right in whatever we say about ourselves, but our self-perception (like all perception) is limited in nature, so how could we ever be sure about who we really are?
Liberalism as the use of irony
In Rorty's point of view, liberalism is a fundamental aspect of human hope, because liberalism is the side of human consciousness that focuses on the way things could be in the future. Therefore, he says that one of the reasons we should be ironic in our self-perception is because it creates a more liberal populace where people are open-minded and willing to be made uncomfortable.
Irony and private allusion
Chapter 6 is called "From ironist theory to private allusions: Derrida." This passage deals with the application of irony in the development of private references. Rorty's point is basically that Derrida is an awesome philosopher because he doesn't even use the pretense of logic in his arguments. He is comfortable using ironic "free-associations" where other people would use logical arguments. Derrida puts irony and allusion about logic and argument.
The irony of morality
Rorty would say that any person's sense of morality would be as subjective as their perception of anything (which is to say it is perfectly subjective). But, in this book, he makes strong cases for lightening up, taking ourselves less seriously, and most of all, trying to become less cruel and more social. It's ironic that a moral relativist would be able to construct such succinct, axiomatic guidelines for human behavior.