Speaker's corner is a public space in London. Traditionally used to give everyone the right to free speech, you can still find people who want to stand up and proclaim to the world something they vehemently believe in. Sometimes it can be funny, sometimes a little crazy; often people here now are of a religious bent, so it depends whether or not you agree with their views as to whether you'll find this entertaining, but nevertheless, it's a free way to pass the time in London and perhaps learn something too, at least about human nature if nothing else. Afterwards you can wander off into Hyde Park for some more free walking through one of London's prettiest parks.