The Lojban MOO The lojban MOO is an ambitious MUD that you should definitely check out!
Nick Nicholas translated the text of Colossal Cave in 1991. Robin Lee Powell has heroically translated that translation into a working game - see Colossal Cave for that, and also for the Inform Localisation files needed to create your own Lojbanic IF.
There is a proposal here for a new game in the works, lojbo munje.
bancus wrote an IRC bot to play a game similar to 5x5 called mumym.
i18n is being implemented for Tremulous. The translation file (.po file) or the vocabulary list needs jbopre to contribute!
Other
A vim syntax plugin enables lojban syntax highlighting an some useful motion commands while using vim text editor.
A vim filetype plugin for convenient word-list lookup, auto-lujvoification, and other useful things.
jbofacki is a jbofihe/camxes CLI shell with Tab-completion of valsi and rafsi, colorized word lookups by literal name or string, etc. Intended for increased fun in exploring the construction of Lojban texts/sentences; also useful as a aid to memory (mi'e la kampu). Requires Python 2.5+, and currently also makfa-cli for generation + update of dictionary data.
Random Sentence Generators
mlismu is Eimi's fact-based lojban random sentence generator. additions to fatci.txt are welcome!
uses jbofi'e to find out which terminators are unneeded