Answer:
For American unfiltered cigarettes avalible today, you have Pall Mall, Camel, Lucky Strike and Chesterfield. Discount American unfiltered cigarettes include Liggett and Pyramid. Some other small name brands make unfiltered cigarattes too, such as American Spirit. English Ovals appear to have been discontinued.
In Canada, you can still buy Player's plain and Export plain in most provinces. Sweet Caporal plain is available in Ontario only (where they are extremely rare). Mark Ten plain and Sportsman plain appear to have been discontinued.