There are standard halflings as a race and using various classes as found in the core materials, but halflings are quite diverse so we'll see how they evolve. I've always noticed, throughout many campaigns, that my players never seem to play as halflings. I think they subconsciously ignore that the entry for them is in the core materials going way back. My best guess for this is because they're attracted to taller, buffer and more obviously glorious character builds. Which defeats the purpose of role playing. These are about taking the little guy and making something big from them. There wouldn't be a Lord Of The Rings without something like that. I know it is arguable as to if Kender from Dragonlance are halflings or not but there wouldn't have been a Tasslehoff1) either if it wasn't for making something big from a little guy. I hope someone picks a halfling some day and does just this.
Please note that for this campaign setting at least, halflings are kind of the mutts of the humanoid world that have mostly devolved in height and primarily take after humans or look like small humans, but their actual ancestory is anyone's guess most of the time, a few exceptions aside where it seems obvious. Halflings are proof of interbreeding between fantasy species, by mundane or magical means.