There’s nothing better than afternoon tea at Mariages Frères, a colonial-style tearoom in Paris. Here I’ve got "smoky Earl Grey" and vanilla-strawberry cake. My friends went for the macarons and scones with their tea. They ordered "black" tea. The waiter, in his snazzy all-white ensemble with bow-tie, sort of smiled, but didn’t press them further (there are about 100 teas available, mostly black, but also green, white and blue). I think they got the house Darjeeling.
The boutique-tearoom is pricey (a pot of tea €8, pastries or cake, another €8), so I only go for special occaisons. There’s also a Sunday brunch that’s quite popular, and lunchtime dishes like salads, quiches, elaborate sandwiches, etc.
I prefer the location in the 6th on the Rue des Grands Augustins (13 rue des Grands-Augustins, tel 01 40 51 82 50), but theone in the Marais (30 rue du Bourg-Tibourg, 4th, tel 01 42 72 28 11) is larger, so you’re more likely to find a table even when it’s crowded.
The teas and accessories (bien sûr!) are sold in Parisian department stores and online, as well.