While you will not find animals that actually sing to their young to soothe them, as most animals do not feel emotion(only prime mates show some signs). Though many animals call to their young as a signal to do something - or to find them.
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If you consider humans to be animals, then of course.

Dolphins and whales also sing songs to imprint on their babies so the babies always know who their mom is. That could be considered a lullaby.
Source(s):
http://www.thenakedscientists.com/HTML/content/news/news/1446/

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Mother birds do indeed sing to their young and nearly every species seems to have some way of communicating with their young. A cat's purring or a dog mother's soft whining or moaning is comforting to their newborn. Female rhesus monkeys attract other mothers' newborns with a form of "baby talk" that serves a similar function to the high-pitched babbling sounds humans make around babies.
Alligators and elephants make rumbling (vibrating) sounds for everything from sending warning signals, to calming youngsters, to mating calls...! Some non-human primates, such as rhesus macaques and squirrel monkeys, make unusual sounds, particularly grunts and nasal whines known as "girneys", in the presence of their infants.

Evidence:
http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db;=PubMed&list;_uids=2792572&dopt;=AbstractPlus
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