We have had some really rainy/damp/humid weather lately, and yesterday I noticed something GROSS on top of the mulch in my flower bed. This morning when I left for work, it caught the attention of both my husband & I because this weird stuff had actually GROWN overnight! After Googling "yellow mold in garden", I found that other people who Garden have also had experiences with this stuff, and what we apparently have is Fuligo septica (dog vomit slime mold). At least it's considered completely harmless, but unfortunately it's also impossible to get rid of according to the Fungi experts. I just hope it will go away and won't spread.