Here are a few of the comics the Squadron Sinister or the various members have appeared in. More detail will be given when I've actually read the comics.
The Growing Man, a tool of Kang the Conqueror, kidnaps Tony Stark, who is in a hospital unconsious and near death. When the Avengers follow, they are swept into the 41st century court of Kang. The Black Panther is there and begs them to listen to Kang for the survival of the Earth. Kang explains that he is involved in a contest with an alien known as the Grandmaster. If Kang wins, he will be given the power of life and death that he can use to save his beloved Ravonna. If he loses, however, the Earth will be consigned to oblivion. The Avengers agree to fight for Earth and Ravonna, but ask Kang to return Stark to the hospital, which he does.
The Grandmaster reappears and asks if Kang has chosen his representatives for this contest. Kang indicates the Avengers and the Grandmaster transports Thor, Goliath, and Captain America to a platform on his tri-sphere and from there to a desert somewhere on Earth. On the ridge above them they see their opponents--Dr Spectrum with his Power Prism, Hyperion, Nighthawk, and the Whizzer--the Squadron Sinister.
Kang is impatiently waiting
Nighthawk's next appearance
Dr. Spectrum's next appearance
Evidently this is where Nebulon hired the Squadron Sinister to destroy the Earth for his personal gain. They were opposed by the Defenders including at least Dr Strange and Yellowjacket. Nighthawk repents of his activities and turns on his allies to aid the Defenders. Dr Spectrum's prism was broken in the fight. When the squadron was defeated Dr Strange cast a spell causing Hyperion, Dr Spectrum and the Whizzer to forget their evil intentions and their super-powers.
After defending the Earth, Nighthawk became one of the staunchest non-members of this non-group, lending his mansion and wealth to their cause.
He might not have joined this book if he knew the changes it would put him through, including: a court order against super-heroing, a power increase-but only at night, becoming paralyzed-but only until nightfall, and having his brains switched with someone else's. Nevertheless, he made many good friends among the Defenders, including Dr Strange, Valkyrie, and Patsy Walker, the Hellcat. Nighthawk died bravely #################106
He is partially resurected in Defenders 108 and takes part in the story line of Defenders 112-115. As it features the Squadron Supreme, it can be found in their bibliography
The first meeting between the Squadron Sinister and the Squadron Supreme. It can be found in the Squadron Supreme bibliography
James Sanders (the Whizzer) re-enters criminal activity under the new codename Speed Demon. He will eventually join an organization known as the Sinister Syndicate, but here is where this page stops tracking him.
As part of a game between the Grandmaster and Death, the Avengers battle what seem to be the incarnated spirits of dead heroes and villians. During the fights, Nighthawk spears Dr Pym and Hyperion drives Wonderman through a planet.
From the way the apparition of Bucky reacts to Captain America, that of the Executioner to Thor, and the Swordsman to Hawkeye, (and a reading of Hamlet) I assume these are not all the true spirits of the people they represent.