In the US there are Direct Investment plans. More than 1,000 US companies offer direct investment plans. Americans can buy shares directly from these companies without using a broker.
In Canada there are no such direct plans so the only way to get shares is to use a broker to buy them, buy from an individual that will sell one, or buy additional shares through a DRiP/SPP. Group buys are a way for individuals to pool their money to buy shares from a broker more cheaply than an individual could because of the fees brokers charge.
Americans can also use Moneypaper to buy shares for them cheaply and to set up DRiPs for them. Canadians can also use this service to get into American DRiPs.
See the Moneypaper Specials board on this site.