I'm sure that I'm missing some, but these are the important ones.

• Writing (2001~now)
• Yu-Gi-Oh! (2003~2006)(2011)
• Japanese language (2004~2007)(2011~now)
• Doujinshi (2004~2008)
• English language (2005~now)
• Cowboy Bebop (2005)
• Mental disorders (2005~now)
• Conlangs (2006~2008)
• Latin language (2006~2009)
• Poetry forms (2007~2009)
• Monster (2008)
• Whose Line Is It Anyway? (2009)
• Inglourious Basterds (2010)
• German language (2010~now)
• Star Trek: Voyager (1996~2001)(2011~now)
• Avatar: The Last Airbender (2011~2012)
• Drew Carey's Improv-A-Ganza (2012)
• Dragonlance novels (2012)