NOTE: The episodes from the album "Odyssey USA" are included in this list since the album is no longer availible.  None of the Family Portraits episodes are availible legally, although a few of their "re-aired" versions are.

3: Lights Out at Whit's End
8: Dental Dilemma
11: Addictions Can Be Habit-Forming
13: Bobby's Valentine
14: Missed It By That Much
15: My Brother's Keeper
16: No Stupid Questions
21: The Case of the Missing Train Car
22: A Simple Addition
23: The Quality of Mercy
24: Gotcha!
25: Harley Takes the Case, Part 1
26: Harley Takes the Case, Part 2
30: Honor Thy Parents
44: It Sure Seems Like It To Me
45: What Are We Going to Do About Halloween?
55: Auld Lang Syne
70: The Return of Harley, Part 1
71: The Return of Harley, Part 2
85: You Go to School Where?
134: Pamela Has a Problem
161: Isaac the True Friend
370: Christmas Around the World, Part 1
371: Christmas Around the World, Part 2
435: A Look Back, Part 1
436: A Look Back, Part 2
438b: The Telltale Cat (Split)
439: BTV: Grace
442b: Sticks and Stones (Split)
444a: Career Moves (Split)
500: 500
501: Inside the Studio

Notes:

Here are some (possible) reasons these episodes are not being distributed:

3: Lights Out at Whit's End -- An Officer Harley episode.  It was not remade. (See this page to see an explanation of "The Officer Harley Incidents".)
8: Dental Dilemma -- This is a remake of one of the Family Portrait episodes, which are in their own album.  It can be purchased on a single cassette from FOTF.
11: Addictions Can Be Habit-Forming -- An Officer Harley episode.  It was not remade.
13: Bobby's Valentine -- An Officer Harley episode.  It was remade as AIO117.
14: Missed It By That Much -- An Officer Harley episode.   It was remade as AIO119.
15: My Brother's Keeper -- This is a remake of one of the Family Portrait episodes, which are in their own album.  It airs on the radio from time to time and can be purchased on a single cassette from FOTF.
16: No Stupid Questions -- This is a remake of one of the Family Portrait episodes, which are in their own album.  It airs on the radio from time to time and can be purchased on a single cassette from FOTF.
17: A Member of the Family, Part 1 -- This is a remake of one of the Family Portrait episodes, which are in their own album.
18: A Member of the Family, Part 2 -- This is a remake of one of the Family Portrait episodes, which are in their own album.
21: The Case of the Missing Train Car -- An Officer Harley episode.  It was remade as AIO118.
22: A Simple Addition -- This is a remake of one of the Family Portrait episodes, which are in their own album.
23: The Quality of Mercy -- An Officer Harley episode.  It was remade as AIO115.
24: Gotcha! -- An Officer Harley episode.  Parts of it were reworked for Curt Stevens in AIO120.  Other parts were "flashbacked" in AIO266.
25: Harley Takes the Case, Part 1 -- An Officer Harley episode.   These two were remade as a single episode in AIO121 and applied to Rodney.
26: Harley Takes the Case, Part 2 -- An Officer Harley episode.
27: A Change of Hart -- ?? This episode does show up on the radio from time to time, but is not available from FOTF.
30: Honor Thy Parents -- ?? This episode does show up on the radio from time to time, but is not available from FOTF.
44: It Sure Seemed Like It To Me -- ?? This episode does show up on the radio from time to time, but is not available from FOTF.
45: What Are We Going to Do About Halloween? -- ??
55: Auld Lang Syne -- ?? Unsure, but like AIO138, AIO167, AIO215, and AIO370 & AIO371 (see below), it doesn't really tell a story related to the storylines in Odyssey.
70: The Return of Harley, Part 1 --  An Officer Harley episode.  These two were remade as a single episode in AIO225.
71: The Return of Harley, Part 2 -- An Officer Harley episode.
85: You Go to School Where? -- ?? This episode does show up on the radio from time to time.  It is available on a single cassette from FOTF.
134: Pamela Has a Problem -- ?? Did they decide against putting this abortion one out because of the "mature nature"? It is available on a single cassette from FOTF.
161: Isaac the True Friend -- ?? We sure would like to hear this one since it introduces Sam Johnson.  It's also the "latest" AIO not released in an album which involves central characters.
167: Dobson Comes to Town -- ?? Not exactly central to AIO stories.
370: Christmas Around the World, Part 1 -- These two were put out on a separate two-sided tape separately.
371: Christmas Around the World, Part 2