Basically, Speakers' Corner is the northwestern area of Hyde Park, near the Marble Arch. It's a place where everybody can take a stepladder, a chair, or whatever and start talking about whatever, and crowd heckles them (the good ones respond to the hecklers). Like everything else, the speakers are covered under Sturgeon's Law, which means 90% of them are rubbish, but even the rubbish ones can be amusing.
Two cases in point: there was this Muslim (probably Pakistani) guy with their weird head-covering and an honest-to-God Abayah who talked about the usual religious stuff; heckling him was a fat, bespectacled and thoroughly unpleasant Briton. As I've said before - YouTube comments, but live and funnier.
The other case was a sort of Evangelist with a huge Bible in one hand; he spent his time shouting through a toothless Egyptian cabbie.
What left me impressed, however, were two guys I met in random. One was born in 1939 and remembers the German Blitz; talk about history (he also believes Jesus converted to Hinduism for some reason, but that's another thing). I met the second guy when I commented to nobody in particular that Abayah guy and his hecklers didn't know how to debate, and this guy agreed with me. Turns out he's from Kuwait, and the sweet part that when I told him I am from Israel, he didn't start spitting curses at me and in fact remained civil and polite. Makes me think there's hope for this place yet.