I think Player of Games by Ian Banks counts. Easily his most accessible work.

http://www.skyhunter.com/marcs/GentleSeduction.html

The Host by Stephanie Meyer. (Yes I know that’s the lady that wrote twilight but this one ain’t so bad)

Cory Doctorow novels

I think Greg Egan's Diaspora would qualify. I've already posted a short review here. I'm not sure if this is what you have in mind for utopian fiction. Basically it's a story about post scarcity humanity.

If this does not work for you, please define utopian fiction a bit more, and I may be able to suggest something else.

SCP 6001 - Avalon is a nice read, especially if you're already familiar with scp

They might not be utopias but I think Neil Stephenson's Seveneves and Andy Weir's Project Hail Mary are both pretty optimistic about cooperation and cleverness in the face of catastrophe.

Island by Aldous Huxley

The Goal

Nick Bostrom's Letter from Utopia Just under 3,000 words. One of my favorite works of writing

Just Another Day in Utopia -- a short story by Stuart_Armstrong on Lesswrong. Pretty direct, succinct take on what experience in a utopian world might be like.

There's a comic by Alan Moore called Marvelman, later retitled Miracleman, that ends in a utopian thing. And Neil Gaiman wrote a follow-up which covers life in the utopia. There are things that are good about it and things that I don't like as much. But I've met other rationalists who like it.
Alan Moore's part was in the 80s, Gaiman's continuation was in the 90s, and then revived and is being further continued as we speak, I think. I like the first part of Gaiman's continuation more than this new stuff.

Have you read Yudkowsky's dath ilan stuff?