The Okuna language (formerly the Tokana language) was created by Matt Pearson in 1993, and has been developing steadily ever since. Matt presented on Okuna (at the time called Tokana—see an early version of the language here) at the First Language Creation Conference (you can see his presentation here), and recently wrote a paper version of his talk (updated to reflect recent changes in the language) which appeared as the first installment of Fiat Lingua (you can download the paper here).
While a website is currently in the works, you can download a grammar and lexicon of the Okuna language in .pdf format here. The .pdf's may be updated from time to time, so check the version number. Both .pdf's may be downloaded below: