Which other ones? There're thousands. Even if you just consider "popular" ones, there're a few hundred, for reasonable definitions of "popular". Very briefly,

Which other ones? There're thousands. Even if you just consider "popular" ones, there're a few hundred, for reasonable definitions of "popular". Very briefly, lojban was conceived as a scientific experiment and tries to re-build the structure of language from the ground up, based on logical foundations with little or no connection to natural languages; the lexicon, however, is derived algorithmically from natural languages, and there is no particular emphasis on concision. Ithkuil, on the other hand, is much more of an artistic project, which makes use of the same basic mechanisms exhibited by natural languages but takes them to extremes in the pursuit of both precision and concision, and has an a-priori vocabulary. Lojban is generally classified as a loglang and an engelang, while Ithkuil is generally classified as an engelang and an artlang. The next most similar conlang to Ithkuil that I know of (and purely in my opinion) would be Latejami by Rick Morneau. Latejami is designed as an interlanguage for translation, and thus doesn't care much about concision (partly because it's mostly supposed to be used by machines, not humans) but does aim to be able to accurately represent any semantic structure that exists in any natlang, and goes to great lengths to systematize its semantics in ways similar to Ithkuil.