Today is Ember Friday. People at St. George keep asking "what are the Ember days?" Here is a quick bullet point tutorial.
1. They happen four times a year, and correspond roughly to the change of seasons (which are actually more accurate as concerns the changes in weather than the traditional "astronomical" dates!).
2. They are always the Wednesday, Friday, and Saturday of the particular week (possibly because fast days were once Wednesday and Friday, and so adding Saturday made it more significant).
3. They are days of penance (which explains the requirement to abstain from meat on Ember Friday). Here is a fun note (thanks Fr. Z): in the sixteenth century Catholic missionaries in Japan got the people to eat fried shrimp on Ember Fridays; the Japanese perfected the shrimp and called it "ember shrimp" (today, called "tempura shrimp"!). If you already practice abstinence from meat every Friday (you do need to abstain from something every Friday of the year--but you already know that, right?) then you are encouraged to do an extra abstinence on the Ember Fridays.
4. The focus is always to use these days to pray specifically for vocations to the priesthood -- mostly those men who are being prepared for ordination, and those who will pursue it in the future, but also your own priest (hint, hint...).
5. Because the summer Ember Days always land right after Pentecost (and because the entire Pentecost week is a solemnity), they are not fully observed (nor is meat abstained from) on that week.
6. Sadly, although not abolished in the Novus Ordo, they were effectively ignored, so most Catholics alive today are completely unaware of this ancient tradition.