Latest updates: February 26, 2018, added "Ai No Kusabi: Space Between- Unchained Edition", the dubbed OVA by Anime Works.
[Click for Ai no Kusabi novel information]1986-1987 Ai no Kusabi (magazine serialization).
This is where the story was originally published over 6 issues of the yaoi magazine Shousetsu June. It includes a few illustrations.
1990 Ai no Kusabi (hardcover).
The 6 parts that were published in the magazine were slightly reedited and assembled into one hardcover book. This version did not have any illustrations.
Translation: A partial fan translation is available here but no longer updated, it was first translated from Japanese to Spanish and then from Spanish to English.
2001-2010 Ai no Kusabi (paperback series).
The story was expanded and some parts rewritten and released as a series of 6 paperback books. Each volume includes several illustrations.
Copyright issues led to a situation in which the paperback series was released by two different companies in Japan, using different illustrations and covers, and the English version is a combination of both of those releases - read more here.
Translation: The series was officially released by DMP manga via their yaoi imprint, Juné, as an 8 volume series. The official English release of volumes 7-8 were found to be very lacking and so there are partial fan translations for important parts: volume 7 misc., volume 8 ch12, volume 8 ch13, volume 8 misc.
Additional languages: French (ongoing by yaoi-ouji).
[Click for Ai no Kusabi anime information]1992-1994: Ai no Kusabi (2 parts).
A two part OVA released 2 years apart.
Translation: A fan translation is available on aarinfantasy. Additional languages: Italian dubbing (official release), French (by yaoi-ouji).
2012: Ai no Kusabi (4 parts).
Known as the 2012 remake, 4 Episodes were released out of 13 planned but further production stopped, apparently due to poor sales and lack of funding.
Translation: There are 2 official English releases - 2013 edition with English subtitles by Media Blasters and 2018 edition with English dubbing by Anime Works, both can be bought cheap at Amazon etc. Additional languages: French (by yaoi-ouji).
[Click for Ai no Kusabi drama CD information]1989 Ai no Kusabi audio book (???An audio book released on cassette???).
1993 DARK-EROGENOUS (Covers Riki’s training. Translation: Yes, here. Check the bottom of the page for the subbed visualization).
2000 Shiozawa Kaneto Memorial (???A digitized re-release of the cassette audio book from 1989??? in memory of voice actor Shiozawa Kaneto).
2007 〜DESTINY〜 (Covers Iason and Riki’s meeting and Riki in the black market. Translation: 1 2 3 4 5 6 7 (in progress)).
2008 〜NIGHTMARE〜 (Covers Riki's time in Eos. Translation: None available).
2008 〜RESONANCE〜 (Covers Riki's time in Eos up until his return to Ceres. Translation: None available).
[Click for Ai no Kusabi soundtrack information]Note: Several tracks on these soundtracks contain character monologues but none of them have been translated yet.
1992 Original Soundtrack
1993 Sense of Crisis
1995 Sound Selections ~Oracion~ (2 CD set)
2001 Music Best ~ Iason
[Click for Ai no Kusabi side stories information]Note: This section is probably missing a lot of information. Please let me know if you have anything to add.
1996 Midnight Illusion (A full length book released in 1996).
Summary: It's possibly a prequel but not much is known about this yet.
Translation: None available.
2010 Illusion Night (A short story published to mark the end of the paperback series in 2010).
Summary: Riki is unsure of his feelings towards Iason after being moved to Apatia.
Translation: Yes, translated by lyrebird.
2012 Daryl short story (Included in the special edition of the 2012 OVA remake DVD release).
Summary: 4 short chapters describing Daryl's life as Iason Mink's furniture.
Translation: Chapter 3: Impulse and Chapter 4: The Night of Disgrace were translated by rainbowfam. Chapters 1-2 have not been translated by anyone yet.
2012 Kizu (Included with the Drama CD 〜RESONANCE〜)
Summary: Bison is celebrating a victory against a rival gang but Riki can't stop thinking about his encounter with a Blondie...
Translation: Yes, translated by lyrebird.
2012 Musk (A short story published in Chara magazine Vol. 25).
Summary: Riki's life after his return to Eos.
Translation: The first 4 pages were translated by rainbowfam and subaru_san. The rest is not yet translated.
Sources: ainokusabi.net, wikipedia, google, this livejournal community.