The alt-right are a young, educated and technology proficient brand of new conservatives. They have no leader. And it's pretty ridiculous to suggest they do. Hillary's conspiracy theory that Putin is somehow in control of the alt-right drew the biggest LOLs from her speech.
The name Milo Yiannopoulos was mentioned above. He could be considered one of the movement's leaders except that he has repeatedly said he is not alt-right.
If you remember those 4 headlines from Breitbart that Hillary read during her speech?
All of them were the names of articles written by Milo. Besides being Brit, he is also gay and makes no secret of his preference for sex with black males. Which puts him in a unique position free from the usual insults and stereotypes lefties love to throw at conservatives.
Milo is bright, funny, irreverent and has a quick wit. His main target seems to be feminists ("feminism is cancer" is his) but he also goes after SJWs alot. He has single-handedly exposed many examples of feminist lying and using fake stats, has caused them to issue retractions, and IIRC caused some to lose jobs. This goes all the way back to Gamergate (which I refuse to try and explain).
He was recently
banned for life by Twitter over the Leslie Jones/new Ghostbusters movie. Twitter never explained this lifetime ban. But it was not for anything Milo wrote himself but rather what other Twitter users did in response to Milo's work (they bombarded Jones with insults). Twitter held him responsible for their behavior.
Anyway, here is an article by Milo himself attempting to explain the alt-right. It should give you all the info you want if you can bring yourself to read a Breitbart housed article.
http://www.breitbart.com/tech/2016/03/29/an-establishment-conservatives-guide-to-the-alt-right/
And here is some video so you can see Milo for yourself
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