To quote the mistake made by the site xrefer.com:
See tigon.

The mistake made is that the liger and the tigon are somewhat opposites of each other.
A liger is the offspring of a male lion (Panthera leo) and a female tiger (Panthera tigris), whereas a tigon is the offspring of a female lion and a male tiger.

Not natural

Ligers (and tigons) most probably do not occur in the wild. For one, the two species prefer different kinds of habitats. The only place in the world where tiger and lion habitats overlap is in the Gir National Park and Lion Sanctuary in India. Apart from that, it's rather unlikely that the very solitary tiger would mix with the rather social lion, which lives in prides.
So the only known examples of tiger-lion hybrids can be found in zoos and big cat sanctuaries1. Enter some of the urls found below to see some great pictures of these remarkable animals.

The largest feline

For some reason ligers are incredibly large, even larger than either of its parent species. The largest naturally occurring feline of the moment2 is the Siberian tiger (Panthera tigris altaica), which can measure 3.30 metres from the point of its nose to the end of its tail and weigh a measly 300 kilograms. Some ligers have been reported to measure more than 3.70 metres and weigh about 500 kilograms.

A little of both

As one would expect, ligers combine a bit of both its parent species, although in general the lion characteristics tend to dominate. This differs with individuals, though.
A liger (and a tigon, too) often has the typical lion tan colouring, run through with faint stripes and spots. The stripes are obviously from the tiger parentage, but the spots come from the lion parentage. Lion cubs are born with spots, which disappear (or probably more accurately: become less visible) when they grow up.
Male ligers sport a mane, though much less impressive than the manes of male lions. The vocabulary of ligers is a combination of lion and tiger sounds, and they may roar like a lion and chuff like a tiger. Ligers have a love of water that they inherit from their tiger parent.

Sterile?

Hybrids, particularly male hybrids, are generally considered to be sterile, but there are some known instances of hybrids producing offspring. All known fertile ligers have been females, so male ligers are probably sterile.
The sterility of male ligers makes it impossible to mate ligers with ligers, so in the cases where female ligers produced offspring the other parent was either a lion or a tiger, thereby reducing the ligerness of the offspring.


Sources:
http://www.sierrasafarizoo.com/animals/liger.htm - liger Hobbs
http://www.loadstar.prometeus.net/tiger/hybrids.html - tiger/lion hybrids
http://www.shambala.org/Animals/patrick.htm - liger Patrick
http://www.tigers-animal-actors.com/tigerinfo/tigerinfopage.html - This page has a picture right at the bottom of a liger. See this one for some perspective on the size of ligers...

1 And maybe (but hopefully not!) in private ownership
2 As opposed to, for example, the previous Ice Age, when sabre-tooth tigers roamed the earth (contrary to what is often thought, this is not one of the ancestors of the modern day tiger)