Witches' Butter, Tremella mesenterica, is a common mushroom that can be found growing on hardwood throughout the year, but I never find it growing abundantly, just isolated little patches like this. (This one's 4 cm across.) A similar species is the Orange Jelly Fungus (Dacrymyces chrysospermus), which grows on conifers and is a bit more orange. An interesting fact about Witches' Butter is that it is parasitic on crust fungi.