The French loan phrase du jour, meaning literally of the day, came to English in the 1960s when restaurants started using it to highlight their daily specials (their plats du jour). More recently, it has expanded from its original sense, and it now sometimes means recent, current, or trendy. But unlike its adjectival synonyms, du jour follows the French grammar by coming after the noun it modifies. For example, you might call a trendy hat the hat du jour, not the du jour hat.
Because du jour has entered common usage, there is no need to italicize it.
Because du jour means of the day, it is redundant when used with today’s—for example:
Today’s O’Donnell Farce du Jour, “I’m You!” — Really? [headline, Fire Dog Lake]
Today’s topic du jour: negative campaigning. [Brattleboro Reformer]
In both of these examples, either today’s or du jour could be removed with no loss of meaning.
Another common error is the mistaken use of de jour in place of du jour—for example:
The latest news from the Gingrich camp is that the GOP front-runner de jour has signed a pledge not to commit adultery again. [Huffington Post]
With brutal tackles the topic de jour in football these days, Young is soon pressed on how much aggression he has had to endure in his career. [Guardian]
And these writers use du jour in the conventional way:
It seems to be the celebrity trend du jour, having your own tiny pet pooch to travel with you at all times. [Daily Mail]
The dish du jour is chicken and egg noodles. [Denver Post]