In the US, you can vote for whomever you want. You just write their name in. And, anyone can get on the voting machines with a prescribed number of signatures on a petition. For instance, Ralph Nader will change from being a write in to a balloted candidate in Texas if he gets 66,000 signatures by May 10. 4 years ago, he was balloted in 44 states.
In Canada there are as many parties are people who organize one. The last election I voted in had (if I remember correctly) Liberal, PC, NDP, Green Party, Canadian Alliance, Marijuana Party, Women’s Party, Marxist-Lennonist Party and Communist Party on the ballot.