Big fan of all the Charlton Characters, your probably aware of most of this but...
Blue Beetle (Ted Kord): To the dismay of a large number of DC fans at the time, Ted Kord had his brains blown out by Maxwell Lord in the mid 2000's, and was replaced by Jamie Reyes as the new Blue Beetle. He has since re-appeared as Ted Kord, and is also currently in the Terrifics comic book. It's not inconceivable that he could get his own Blue Beetle run again, which would be nice, so long as Jamie Reyes is not sidelined and is active in a comic somewhere.
Blue Beetle (Dan Garrett) I haven't read the Jamie Reyes runs, but it is my understanding he showed up there at one point, otherwise I have no clue on his status.
Blue Beetle (Jamie Reyes) Still active as the Blue Beetle, had his own run a while back, I'm not sure where he is currently being used, but I imagine he will pop up as part of super hero team soon, if he isn't on one already.
Captain Atom: Still kicking about to my knowledge, always used as a metahuman big gun.
The Question (Vic Sage) As noted, was killed off in the mid 2000's shortly after Ted Kord, but has been resurrected. He first started to show up in Superman titles of all places, and then Event Leviathan, and he now currently has his own quarterly mini series, that harkens back to Denny O Neil's style. Personally, I would like to see him used more in the DC universe (Aka JLA cartoon). I'm not sure if your referring to Vic or Renee, but as a major Vic fan, I would love to see him in the back pages of Detective Comics.
The Question (Renee Montoya): Still around, I believe she is in the Harley Quinn and Birds of Prey comic.
Nightshade: She showed up in Justice League Dark a while ago to my recollection. When DC bought Charlton Comics back in the 80's the readership was still predominantly male at the time, unlike today where they females make up to 40% of comic readers (Though I do not know if they are reading superhero comics) which is probably why she never got her own mini series, but I definitely would like to see her used more.
Peacemaker: I've always had a soft spot for this character, largely because I happen to have his first comic, which is worth, and will always be worth...didley. He had a mini series at one point, but otherwise he is hardly used by DC. Surely he would be a good fit for a team like Checkmate?
Judomaster: The first Judomaster was killed off in Crisis on Infinite Earths around the time DC bought Charlton...so not a good start. Today Judomaster is female character, who I think would be a great fit for showing up in Batgirl (Cassandra Cain) comics, but she needs an overhaul on her uniform first.
Thunderbolt: I didn't even know this guy existed. So Cudo's for the person who filled his current status in.