167 rue Saint Denis, Paris.
My friend brought me to this little place and it is amazing. You could easily walk past it, it is so unassuming, but make sure you go in. They do breakfast and lunches, and although at first the menu might seem a bit pricey, the food is so worth it. They do fried breakfasts with hot chocolates and fresh fruit juice and amazing jams as well as salads for lunches and some really nice teas. The people who work there are so friendly too and were so patient with our poor French, which is such a bonus! Again, I've heard that it gets very busy around lunchtime; we went in about 2pm and we got a seat no problem.
Keep an eye out for... the breakfast deals, especially the selection of bread and 'confiture' which come too!