The Smithsonian.com has a short article about him, which contains a couple of surprises (he was allowed a conjugal visit with his wife, but she was an unfaithful alcoholic; and he kept a journal while in prison that indicates he may have had a touch of Stockholm syndrome.)
His son has a website up, which doesn't have a lot of content, but some of it is interesting.
As for the old poison needle in the coin trick: yes, this was true and the poison used was saxitoxin, derived from shellfish.
You can even read an account of his accident on the CIA website, where we get a good description of his dangerous exit from the U2:
The young pilot had been flying for almost four hours when he heard a dull thump, the aircraft lurched forward, and there was a bright orange flash from a nearby surface-to-air missile. The plane’s right wing began to droop and the nose started to go down. Powers tried to correct it, but the plane continued its downward trajectory. Powers was uncertain if the control cable had been severed or if the tail was gone. He was certain, however, that he no longer had control of the plane.Maybe not exactly as portrayed in the movie, but pretty close.
Powers initial reaction was to pull the destruct switches, but he decided he’d better secure an exit plan for himself first. This, however, was proving difficult as the g forces had hurled him to the nose of the plane, which was spinning tail first towards the earth. Powers thought of ejecting but realized, in his current position, he likely would have had both off his legs cut off while trying to escape the plane.
On the verge of panic, Powers decided he would climb out of the plane. The whirling aircraft had passed thirty-four thousand feet when he removed the canopy. He took off his seat-belt, which sent him flying halfway out of the aircraft. His face plate frosted over rendering him visionless. Powers tried to get to the destruct switches twice but, realizing time was running out, he began kicking frantically and miraculously the oxygen hoses that were holding him hostage in the U-2 broke and freed him from the spiraling plane.
Suddenly, all was silent, except for the rustling of material as the chute opened and settled in the wind. Powers hung in the air desperately trying to comprehend what had just happened and trying to assess his current situation. He was fifteen thousand feet above the Soviet Union and the ground was growing ever closer. As he clutched the straps of his chute, he saw a piece of the plane float down past him.