I am a big hard science fiction fan (that's [big [hard science fiction] fan], not [big hard [science fiction] fan], and I am especially interested in utopic settings. They are not only entertaining but inspiring, in my opinion. I of course define "utopic" as "utopic from a utilitarian perspective".

One of the most well-known modern utopic settings is Iain M. Banks' The Culture. A famous "flawed utopia" is the society portrayed in Aldous Huxley's Brave New World. Can you think of any further examples?

Greg Egan is a great science fiction author, with frequent utopian and philosophical themes.

In fantasy, I cannot recommend Eliezer Yudkowsky's Harry Potter and the Methods of Rationality highly enough.

Kim Stanley Robertson's Mars Trilogy sort of fits the bill (though it's quite a spoiler to say so :\) - it culminates in an imperfect utopia. Unfortunately he tries to reinvent the wheel, and dismisses an obvious improvement to the social metric he advocates as ‘just regressing back to utilitarianism’, or something to that effect (his proposed ethic is to maximise the number of calories everyone contributes in net to the economy).

Thanks for your tips!

I think Skinner's Walden Two fits your description.
http://en.wikipedia.org/wiki/Walden_Two