Some die-hard knitters turn their nose up at acrylics, but these fibers have come a long way. There's still nothing natural about them, but they more closely mimic some of the natural fibers these days.
The upside of acrylic is that it tends to be inexpensive and is machine washable. It's great for baby gifts because the new mother doesn't have to worry about how to care for it.
Acrylic yarn comes in a dizzying array of colors, textures and weights. It can be a lot of fun to work with because acrylic can do things that natural fibers can't do. Many of the novelty yarns are acrylic, and these yarns are a lot of fun to work with for a scarf, handbag or other fun accessory.