This is shaping up to be a great resource.
Yet another interesting list: http://hanna-barbera.wikia.com/wiki/Category:Cartoons_not_yet_on_DVD
A few more…
Coast to Coast (1987) - a road movie comedy co-produced by the BBC with John Shea and Lenny Henry in the lead roles. Hugely popular but it has never received further airings or a home video release of any kind, ever. The production company and Lenny Henry have confirmed that this situation will probably never change as the extensive usage of Motown songs for the soundtrack would cost the BBC hundreds of thousands in re-licencing fees.
Seasons 3 to 6 of Judging Amy. The first two seasons are available on DVD but with the soundtrack altered due to licensing issues. Lead actress, Amy Brenneman has attributed the lack of a complete release to intransigence between the drama’s co-producers, Fox and CBS.
Muppet Babies - I haven’t been able to watch this since the mid 80s when the BBC had the rights. Even on VHS, it had a patchy release history. Again, licensing issues are an obstacle to any DVD/Blu-Ray release because of the sheer volume of the film clips that were used during each episode. However surely an organisation such as Disney has the resources to get this resolved? Especially now that they own Lucasfilm.
Doublecrossed (1991) - HBO biopic starring Dennis Hopper as Barry Seal, a drug/gun runner, turned DEA informant and undercover operative. Available on VHS and LD but nothing since.
The uncut (not the NC-17) version of Ken Russell’s “Whore” (aka “If You Can’t Say It, Just See It”) has only ever been issued on NTSC VHS.