People watching is one of my favourite weekend pastimes and the Parisians sure do have it down to a fine art.
One of my favourite streets to wander and people watch would have to be Rue Bonaparte. This delightful street is situated in the 6th arrondissement and is lined with adorable cafes such as this one (located right near Place Saint - Sulpice), great art galleries, amazing bookshops, and some of the yummiest sweet treats to be found in Paris.
Also if you are a fan of French pharmacy skincare and beauty products this street is right up your alley with one of the cheapest (and subsequently often most crowded) pharmacies in Paris, City Pharma. It helps if you do you research first as to what you are after as it can get pretty crazy at times, however the great price points make it worth a visit.
For those after something on the sweeter side you have some pretty dreamy choices on this street including Ladurée, Pierre Hermé, and many others. Not to mention with the Jardin du Luxembourg on one end of the street and the River Seine (near Pont des Arts) on the other you have some pretty incredible places to stop by and enjoy your treats. Of course that's if they make it that far...no judgement here.