Grey Company Elvish
Grey Company Elvish, nicknamed Grelvish among Tolkienists, was an Elvish conlang developed and used by the Grey Company (Tel'Mithrim), a guild of Ultima Online players who play Elves; it is not to be confused with any of Tolkien's Elvish languages, though it is in part based on them. Its main purpose was to give flavour to in-character dialogue. Alas, the Grey Company's web site is gone, so they probably aren't active anymore, and the language is lost.
Grammar
The grammar of Grey Company Elvish is mostly analytic and weakly agglutinating. There are several plural suffixes (-r, -ea, -ie, -or, -io, -oo), "exact choice is left to the person creating the plural". A suffix -rim is used for great numbers or respect. The pronouns distinguish case only in the third person. Possessive pronouns are suffixed to the possessed noun. Verbs distinguish present, past, future and conditional, but do not receive person/number marking. Word order is SVO.
Lexicon
Grey Company Elvish uses a vocabulary based on elements from Quenya (e.g., calma 'lamp') and Sindarin (e.g., amon 'hill'), but also from various other sources which are not always easy to identify; one of them seem to be various Dungeons & Dragons roleplaying handbooks (e.g., Tel'Quessir 'the Elven race'). There also appear to be some Celtic bits in the lexicon (e.g., shee 'fairy' from Irish sidhe).
External link?
The old link no longer works, another one I had doesn't, either. Does anyone know a web site where this stuff is now hosted? (But well, it was dreadful enough, so I don't really miss it.)