Where do I post? Well, in Pokécommunity... ;)
Other than that, I post some of my stuff in AO3 (Archive of Our Own) because of the simplicity to add works (rich text formatting, categories, tagging, etc).
I used to post at Serebii, but over time it seems that the writing community there has died, and not even me trying PMD fics (the usual "guaranteed replies" of the site) gets me any new attention, so I've though of dropping Serebii altogether just like Bay said. In exchange, I've slowly migrated to Canalave, I like their simplicity and the fact that you don't actually need to post there (saving you one formatting nightmare) but instead you can actually integrate your AO3 stuff. IMO, more sites should do that.
I've... thought, actually, of posting on DeviantArt. Yes, despite the annoying UI and the slow-as-lolasses site. Please don't let me fall that low.