When fresh and young this slime mold does, indeed, look a bit like a raspberry. However, like most slime molds Tubifera ferruginosa goes through radically different stages of development, and its pre- and post-raspberry stages (see the illustrations below) are not very raspberryish.

Look for raspberry slime mold on well rotted wood during, or just after, wet weather. We find it on the deadwood of hardwoods, but it is often reported in the literature as appearing on conifer wood, as well. If your interest in slime molds is more than casual, we should let you know that this is actually a group of species (there are about a dozen worldwide, and many of them appear in the Midwest), best separated by microscopic analysis and very careful attention to the physical details of the fruiting bodies; see Leontyev et al. 2015 for an identification key and species descriptions.