I noticed that the URL of each lesson includes a date (I guess, when it was uploaded?). So, I decided to make a list of all the seasons on JPod101 in chronological order (going by the date of the first lesson in each season).
2005 December - Introduction (Intro: Audio)
2005 December - Survival Phrases S1 (AB: Audio)
2005 December - Just for Fun (AB: Video)
2005 December - Beginner S1 (Beginner: Audio)
2006 January - Culture Class (Intro: Audio)
2006 February - Intermediate (Intermediate: Audio)
2006 August - iLove J-Drama (Intermediate: Video)
2006 August - Advanced Audio Blog 1 (Advanced: Audio)
2006 October - Lower Intermediate S1 (Intermediate: Audio)
2006 November - Beginner S2 (Beginner: Audio)
2006 December - Newbie S1 (AB: Audio)
2007 July - Newbie S2 (AB: Audio)
2007 August - Extra Fun (Bonus: Audio)
2008 January - Newbie S3 (AB: Audio)
2008 January - Beginner S3 (Beginner: Audio)
2008 January - Lower Intermediate S2 (Intermediate: Audio)
2008 January - Upper Intermediate S1 (Intermediate: Audio)
2008 May - Journey Through Japan (Intermediate: Video)
2008 July - Newbie S4 (AB: Audio)
2008 July - Beginner S4 (Beginner: Audio)
2008 July - Lower Intermediate S3 (Intermediate: Audio)
2008 July - Upper Intermediate S2 (Intermediate: Audio)
2008 July - Yojijukugo (Bonus: Audio)
2009 January - Kanji Videos with Hiroko (AB: Video)
2009 January - Video Vocab (Beginner: Video)
2009 January - Lower Intermediate S4 (Intermediate: Audio)
2009 January - Upper Intermediate S3 (Intermediate: Audio)
2009 January - Advanced Audio Blog 1 (Advanced: Audio)
2009 January - Onomatopoeia (Bonus: Audio)
2009 July - All About (Intro: Audio)
2009 July - Survival Phrases S2 (AB: Audio)
2009 July - Everyday Kanji (Beginner: Video)
2009 October - JLPT S1 - Old 4/New N5 (Bonus: Audio)
2009 November - Learning Japanese through Posters (Intermediate: Video)
2009 December - Japanese Body Language and Gestures (AB: Video)
2009 December - Japanese Children’s Songs (Bonus: Audio)
2010 January - Newbie S5 (AB: Audio)
2010 January - Basic Japanese (AB: Video)
2010 January - Beginner S5 (Beginner: Audio)
2010 January - Lower Intermediate S5 (Intermediate: Audio)
2010 January - Upper Intermediate S4 (Intermediate: Audio)
2010 January - Advanced Audio Blog 3 (Advanced: Audio)
2010 January - JLPT S2 - New N4 (Bonus: Audio)
2010 January - Particles (Bonus: Audio)
2010 July - Kantan Kana (AB: Video)
2010 July - JLPT S3 - New N4 (Bonus: Audio)
2011 January - Absolute Beginner S1 (AB: Audio)
2011 January - Learn with Pictures and Video (AB: Video)
2011 January - Beginner S6 (Beginner: Audio)
2011 January - Lower Intermediate S6 (Intermediate: Audio)
2011 January - Advanced Audio Blog 4 (Advanced: Audio)
2011 January - Cheat Sheet to Mastering Japanese (News: Audio)
2012 January - Absolute Beginner S2 (AB: Audio)
2012 January - Learn Japanese Grammar Video (AB: Video)
2012 January - Upper Beginner (Beginner: Audio)
2012 January - Upper Intermediate S5 (Intermediate: Audio)
2012 January - Advanced Audio Blog 5 (Advanced: Audio)
2012 July - Learn with Video (Beginner: Video)
2013 January - Culture Class: Essential Japanese Vocabulary (AB: Audio)
2013 January - Lower Beginner S1 (Beginner: Audio)
2013 January - Advanced Audio Blog 6 (Advanced: Audio)
2013 January - Video Culture Class: Japanese Holidays (Advanced: Video)
2013 July - Japanese Counters (Beginner: Video)
2013 October - Japanese Listening Comprehension for Beginners (Bonus: Video)
2014 January - Top 25 Japanese Questions You Need to Know (AB: Audio)
2014 January - Ultimate Japanese Pronunciation Guide (AB: Video)
2014 January - Japanese for Everyday Life LI (Intermediate: Audio)
2014 January - Inner Circle (Bonus: Audio)
2014 January - Japanese Listening Comprehension for Absolute Beginners (Bonus: Video)
2014 March - Japanese Listening Comprehension for Intermediate Learners (Bonus: Video)
2014 April - Japanese Listening Comprehension for Advanced Learners (Bonus: Video)
2014 July - Culture Class: Holidays in Japan (Intro: Audio)
2014 October - Innovative Japanese (AB: Video)
2014 October - Japanese Words of the Week with Risa for Beginners (Beginner: Video)
2014 October - Japanese Words of the Week with Risa for Intermediate Learners (Intermediate: Video)
2014 October - Must-Know Japanese Holiday Words (Intermediate: Video)
2014 December - AB Japanese for Every Day (AB: Video)
2015 January - Lower Beginner S2 (Beginner: Audio)
2015 April - AB Questions Answered by Hiroko (AB: Video)