I'll start myself: I've been quite interested in Esperanto recently, and I am thinking of starting to actually learn the language. Esperanto is just really interesting to me, because of its history and size, compared to other conlangs. I don't believe it will become the universal world language, like once was dreamed. And I do think esperanto has quite a few shortcomings when it comes to being an international auxilliary language. The reason I want to learn it is more just for that history and culture.
I speak some bits of Esperanto. Simple sentences, really; "mi nomiĝas [enmetu nomon]" tier. I could've progressed further on it if I wasn't prone to the "oooh shiny" syndrome, and Sanskrit didn't take so much of my time back then.
I also can read and write Tengwar, but I don't know any conlang using it, not even Sindarin. (I use it mostly with Italian and Portuguese)
Beyond that I'm trying to learn the basics of my own conlangs Tarune and Meznagar as I'm making them. Specially the later as it has a bit more of a normal phonology, the former has stuff like pre/post-nasalised stops and uvulars that give me a hard time.