It seems as if everyone in the whole county of Maycomb is affected by Tom Robinson's trial, but, of course, those closest to him suffer the most—specifically, Tom's family. His wife Helen has three kids who she has to raise all by herself after Tom is killed trying to escape from prison. Fortunately, Link Deas gives Helen work so she is able to provide something for her children.
Since the story is written from Scout's perspective, the reader sees mostly how the trial affects her and those around her. It's interesting that Scout isn't more affected than Dill and Jem, because she doesn't cry over the trial, the boys do. Dill doesn't even make it through Mr. Gilmer's cross-examination of Tom before he's crying uncontrollably and Jem sends him out with Scout. Dill protests as follows:
"'It was just him I couldn't stand,' Dill said. . . . 'That old Mr. Gilmer doin' him thataway, talking so hateful to him. . . Mr. Finch didn't act that way to Mayella and old man Ewell when he cross-examined them. The way that man called him "boy" all the time an seered at him, an looked around at the jury every time he answered'" (198-199).
The above passage shows Dill's first experience with real evil and the disrespectful behavior of someone who is bent on doing evil. Mr. Gilmer probably guts Dill's hope for humanity for a bit.
Next, Jem is affected by the trial for months after Tom's conviction. In fact, Atticus and Jem have extensive conversations about what happened during the trial and as a result thereof. Jem can't grasp how unfair the whole trial was and Atticus explains as follows:
"'The older you grow the more of it you'll see. The one place where a man ought to get a square deal is in a courtroom, be he any color of the rainbow, but people have a way of carrying their resentments right into a jury box'" (220).
Finally, there's Atticus. He knew he wouldn't win Tom's case on the first try. His greatest hopes were on the appeal process and he told Tom to hold out for that. Atticus was a true defender of not only Tom but what the trial could have represented for future generations if the appeal would have overturned the prior conviction. As a result of his great efforts, Atticus didn't take care of his mental and emotional health as he normally would have, and Alexandra was the one to let Maudie and Scout know about it:
"I can't say I approve of everything he does, Maudie, but he's my brother, and I just want to know when this will ever end. . . . It tears him to pieces. He doesn't show it much, but it tears him to pieces. I've seen him when—what else do they want from him, Maudie, what else?" (236).
Atticus wasn't thinking of himself, but if he had won on the appeal, that would mean that the South could change and actually give everyone a fair trial in the court system. So much progress could have been made for the black community with a win. Poor Atticus had to wait a long time for that.