Blood, which is a mix of many components, both cellular and chemical, behaves like many other salty (saline) solutions and freezes at between -2 to -3 degrees celsius.
Normally however, each unit of whole blood is separated into several components: Red Blood Cells, which may be stored at 4 degrees C for 40 or so days, or frozen (generally at -79 degrees C) for up to 10 years.
Platelets (functional in the control of bleeding) are stored at room temperature and are generally kept for a maximum of five days.
Blood Plasma (the chemical-rich media in which the cells are transported), is usually kept in the frozen state for up to one year.
So -2 /-3 degrees, but it is not generally held at this temperature in terms of storage.
If you're talking animals in general, it may be worth my mentioning that under special experimental conditions, antartic fish have been observed functioning in ice-free cold salt water at a temperature of -6°C thanks to anti-freeze proteins!
It freezes at around -2 and -3 degrees Celsius.