The area sometimes known as the horn of Monoceros is replete with star clouds, clusters, and emission nebulae.  The most famous is the Rosette Nebula, the bright red "rose"-like structure at center right.  It enwreaths the open cluster NGC 2244 and abuts NGC 2252 as well.  The region around NGC 2264, also known as the Christmas Tree cluster, is awash in faint reddish nebulosity, which barely shows up on my 120 second image stack.  Very small but bright is NGC 2261, called Hubble's Variable Nebula, a very interesting object and easy to study in a moderate sized telescope.  Unannotated image.