Cthulhu's Librarian said:
What are the important Holidays and Festivals in your world?
There are a bunch - mostly religious feast days or special historical anniversaries. Things like the founding of certain religious sects, the death date of various saints or prophets, the anniversary of the recovery of sacred relics, that kind of thing.
Are they different as you go kingdom to kingdom?
They mainly differ for the different world religions. "The West" pretty much all share a version of the same religion so their holidays are all very similar. Regional variations creep in depending upon which "saint" is more popular in a particular country, city, or village. King's and Queen's birthdays are also often celebrated as holidays, as are the various founding dates for each country.
Are any of them celebrated the world over?
Not really. The equinoxes and solstices are usually celebrated, but they end up being tied to religious services and since the religions are all so different, the celebrations end up being very different.
Are there any that are unique to the various good races? what about the evil races?
My world is pretty much all shades of grey so this question doesn't really apply to me. My races tend to be more integrated, so you get elves and dwarves and goblins living alongside humans in big urban areas so they all end up pretty much sharing the same holidays. Some races prefer to try to keep their cultural identity but they're on the losing side of that battle.
What holidays are the governments of the world trying to stop?
Anything that they church tells them is bad.
Are there any that used to be celebrated, but are now just a memory?
Sure. The group I DM is not really super concerned about such stuff, though, which is too bad. Many past celebrations are rooted in historical mysteries that could provide clues for their current adventures, but they just don't seem to want to try to immerse themselves in the world like that, so I just let it go.