The Flash
The Flash - The Complete Series IS in the works, and WILL be on DVD in the future! The studio hasn't revealed much officially about it at this time, so the release date and any other details are yet TBA.

The 1990 series starring John Wesley Shipp as "Barry Allen/The Flash" and Amanda Pays as "Tina McGee" was short-lived (22 episodes) but has become a fan favorite. The show was based on the classic DC Comics superhero about a police scientist who gains super-speed in an accident involving lightning and chemicals, and who uses his powers to fight crime. M. Emmet Walsh, Jason Bernard, Angela Bassett, Priscilla Pointer, Denise Crosby, Jeri Ryan, Bill Mumy, David Cassidy as "The Mirror Master", and Mark Hamill as "The Trickster" are among the many guest stars in this cult classic.

Also, the September 13th release of Smallville: Season 4 includes a bonus DVD featuring an episode of The Flash, so pick that up if you want to get a taste of the set to come.

Source: TV Shows on DVD