Some of these hit close to home, from The Catholic Nerd Blog by way of Happy Catholic:

...you can rattle off the times for every Sunday and Daily Mass in town.

... you feel guilty for missing daily Mass.

… your most common phrase at parties starts with “Well, the Catholic Catechism says …”

... your dress shoes are all scuffed on the top of the toes from kneeling at church.

... somebody tells you they want to be a saint and you take them seriously.

... you dress to match the liturgical season

... you pick dates for significant events by looking up feast days.

... you know which Eucharistic prayer is being used in 5 words or less.

... you know the words to Tantum Ergo, Salve Regina, Ave Maria, Agnus Dei

... you remember the names of the apostles by going through your brothers

... you still sing "saved a wretch like me" and other un-PC lyrics -- if you are actually singing, you already knew you are an odd Catholic.