I've just starting reading 'A Brief History of The Wars of the Roses' by Desmond Seward, so I only have a brief outline of what happened in the Wars, but Richard III has been in the news lately and everyone seems to be praising him, and some people talk about the injustices he faced.
Since I'm not that educated on the matter, the most I know is that after his brother died, he took the crown, and claimed that his brother's marriage was illegitimate, so that Edward IV's sons couldn't claim the crown. He has also been accused of killing the princes in the Tower of London.
From that, it seems as though he wasn't really a fair king, even for those times, but again, since I barely know anything about him apart from the bad things that he did, what did he do that makes people love him and praise him so much now?
Probably the biggest reason for interest in him recently is that his body was recently discovered. However, since this is a recent event I won't discuss it further.
You'll find a lot of information about the work being done to restore his reputation at the Richard III society online, who state that "Richard's infamy over the centuries has been due to the continuing popularity, and the belief in, the picture painted of Richard III by William Shakespeare in his play of that name. The validity of this representation of Richard has been queried over the centuries and has now been taken up by the Society."
If you haven't read the Shakespeare play I would also recommend that as it will give you a background into why people might feel motivated to support Richard as a historical figure. In short, Shakespeare's Richard is an absolute bastard. He is seductive, murdering, power-hungry, greedy, and he makes the audience complicit in everything he does. Although it was a history play Shakespeare blames many deaths and actions on Richard that were in no way attributable to him. Richard probably ordered the deaths of the princes but that pretty much puts him on par with everyone else involved with the war of the roses. Contemporary sources generally portray him favorably as a ruler.
A major reason for making him so contemptible in the play is because of the time it was written. Because of the belief in the divine right to rule regicide was a crime against god as well as man. Shakespeare had to make Richard the most horrible villain he could so that when Richmond kills him the act is totally justified (rather than being the highest crime in the land). Richmond's granddaughter, Elizabeth I, was queen at the time and to question Richard's wickedness was to question the legitimacy of the Tudor line.