The fellow at the top is Hank Saroyan, the director/producer/guiding force through most of the series. I'll bet he also snuck in and did some voices, too, since he has voice credits in other cartoons later on, according to the IMDb. He also directed "Muppet Babies."

Second row:

• Peter Cullen, voice of Venger and a number of incidental characters throughout the series (Rahmoud is one example). Peter is probably better known for his roles in the Transformers series, where he voiced Optimus Prime and various others. He also sounds very entertaining: read a transcript of Cullen's appearance on a panel at BotCon 97.
• Katie Leigh, voice of Sheila. She has worked on a number of other cartoons, notably "Muppet Babies" (Rowlf), "My Little Pony" (Fizzy and Baby Sundance), and "Slimer! and the Real Ghostbusters" (Jason the Junior GB). Katie has a fan club! Click here to visit, and read her thoughts on reconciling being a Christian AND a D&D star.
• The tall guy behind Katie is none other than Willie Aames, voice of Hank, star of "Charles in Charge" (Buddy Lembeck) and "Eight is Enough" (Tommy Bradford). After a bad bout with drugs and booze he cleaned up his act, and is now the one-and-only Bibleman! You can also check out the Willie Aames worship page, which is far more entertaining...
• The elusive Tonya Gail Smith, voice of Diana. As far as we can tell, Tonya vanished off the face of the Earth (or at least voice acting) after the series ended, and no other information is available.
• Adam Rich, voice of Presto. Adam was also a star of "Eight is Enough" (Nicholas Bradford). He was 14 when the D&D series began its run in 1983. Now he works behind the scenes, according to this EIE website I found. Adam pulled a bigger stunt than Presto's "Whirlwind of Doom" when he let "Might" magazine publish news of his untimely death, a bad practial joke that lost him a lot of fans....but we forgive him, don't we?

• Donny Most! Ralph Malph on "Happy Days," would, of course, be his most memorable role. Here he is today! I'm still digging up info on his current affairs, but here he is back in 1999, in Italy at the premiere of some show or another, courtesy of the international Happy Days Fan Club.
• The ubiquitous, the one-and-only, the man who can be ANYTHING: Frank Welker! He voiced Uni and Tiamat and probably eight dozen other characters. Got his start in 1969 as Freddy Jones in "Scooby Doo, Where are You?" and has done hundereds of vocal effects since. Read a great interview with this dynamic fellow here.
• Sidney Miller, voice of Dungeonmaster. According to the IMDb, he was born in 1916 and had an extensive career of acting and composing, before getting into voice acting.

• Teddy Field III, voice of Bobby. Teddy, or Ted, as he probably prefers at this point, has also dropped out of Hollywood, and no 'official' information is available on him. However, someone claiming to be him stopped by the old Helix town square at one point, to give us an update on his life. He is apparently just out of dental school, and married. I shall never forgive Beseen for crashing and losing that message! Grrrrr!

• Bob Holt did the voice of sneaky ol' Shadowdemon. He has a boatload of voice credits starting in 1950 that I'm not going to list here. Unfortunately he passed away in 1985.
• Mark Evanier (that's pronounced ev-uh-near, I found out) was the guy who simplified and revamped the concept of the show, rescuing it from certain oblivion (he downplays his role, though...*g*). Read the story of D&D's birth, and why Mark detests Eric but had to leave him in, in his article 'No Way Out.' And don't pester him about Michael Reaves posting the final episode, he already knows, thankyewverymuch- this article was from 1997.
• Dennis Marks was the original creator of the D&D show. I know nothing more about him, save that he's worked on many, many shows since.