Another fun question!
Hmm, worldbuilding...that's a word that seems to call to mind fantasy writers specifically, and obviously that's the main place you have to do it. I tend to like settings that are mostly like the real world but with fantastic elements or twists (gee, I guess that's the answer to the genre question that I was wishy-washy on a few days ago) so my job tends to be to build the parts of the "worlds" that make it distinct.
My two examples of this are, of course, Defying Gravity and Altitude. Or, since I like to go by the main character's first name, Azilie's story and Celeste's story.
I'm pretty pleased with the comments I've gotten on DG so far, where people note the things they've noticed are different, and they like them and it makes them want to know more. For example, the puffs that the kids have above their heads. Everyone seems intrigued by the puffs. The various abilities that kids have also seems to be working for the readers, and of course, the fact that kids lose these abilities at a certain age.
I guess there aren't that many details to build in that world, when I write it out...what I'm proud of is that I seem to be succeeding in letting these unfold naturally/unobtrusively. The whole "showing not telling" thing. And people seem to follow it. So I'm pleased.
In Altitude, Celeste actually has to be told a lot of stuff herself, so that makes it somewhat easy for me to show things to the reader. I try to be careful not to go overboard on the politics of the various nations involved in this story, since I know that bores just about everyone but me, but some of it is of course necessary. But in that case I tend to work it in just like something you'd hear on the news in a story set in the real world, and I seem to be doing okay with it.
And now I'm off to do some writing on a story set in our real world!