It depends which country you live in.
Outside Lent Friday penance is obligatory but some countries require abstaining from meat to be the penance while other countries (most actually) allow any form of penance to be done.
Although I believe just recently (September of 2011) England and Wales ‘reinstituted’ the discipline of abstinence from meat on all Fridays which again I believe is the ‘default’ norm of the Church unless the given bishop in a given area/country has been granted an indult.
Personally I’d like to see year-round meatless Fridays again. It’s a great tradition and a nice ‘visible’ Catholic identity sign.
And I say this as somebody who hates and detests fish and isn’t all that great on vegetarian foods. There is no need to go out and dine on lobster thermidor --having a light dinner of scrambled eggs and toast, or sitting down with vegetarian chili, or a large healthy salad, is eating ‘normally’ enough yet with some mindfulness. And if you’re already vegetarians, you have the option to eat LESS or to eat along with your usual meal something you aren’t too fond of but which is not junk. Maybe you really don’t care for squash unless it’s in the form of pumpkin pie, but if you have a large family you can cook a small acorn squash and take a few bites each Friday. This would definitely get you feeling penitential and mindful.
Or you could always PLAN a lobster dinner (if you love seafood of all types) and then sit down to plain boiled cod. You love seafood but if you have (in your imagination) prepared yourself for lobster and all the trimmings, you’ll be eating your cod (which you like) but you won’t be eating the lobster which you LOVE. And you’ll have some feeling of sacrifice.
In any of the cases, what we’re aiming for is giving up something GOOD for something which is, to us personally, LESS desirable, and doing it out of love for God.
I know that probably most Catholics are, on a given non Lent U.S. Friday, chowing down on beef without a qualm (and I love beef), even though they probably pray just as much as I do, go to Mass regularly or semi-so, think about and love God as much as I do, etc. They probably do a better job as Christians at any given minute than I do so I’m not being holier-than-thou; it’s just I believe that a non-meat Friday all year gives Catholics the heaven-sent opportunity on EVERY Friday to offer something to God and think about Him. I think we could use more of those opportunities. And we might start seeing more people coming to weekly Masses if we bring back some of the practices we had as Catholics and make them visible. It could be worth a try.