Although it won’t grow new hair on a totally bald scalp, Rogaine foam 5% (Minoxidil) is a very good product for maintaining hair. I use it at least three or four times a week. For best results, you are supposed to use it twice per day, but I never use it more than once a day.
Unlike the old liquid version, the foam does not cause a mess or trickle down your face or back of neck, dries rapidly, and actually holds your hair like a weak gel.
Amazon currently has an incredible sale of one can for sale at only $10 (usual price = $30). Note that there are only limited quantities available:
Edit: Seems like the product is sold out at that price. Some decent discounts still available for 3-month supplies shown in the photo above.
Rogaine Foam in Canada
Note that sometimes, you can find Rogaine foam for sale in Canada. At the moment, 1 US dollar = 1.32 Canadian dollars. The three can product is more likely to be on sale than the one aerosol can version.