Before Jabba the Hutt was an infamous crimelord, he was a mercenary and a gunrunner. He often worked with Ephant Mon, who we saw in Return of the Jedi in Jabba's Palace. Before his crimelord days Jabba worked for his uncle Jillac, whose empire he eventually inherited and expanded. (Sources: Paradise Snare, Jabba comics, The Hutt Gambit)

Jabba was not always as fat and out of shape as he appeared in Episode VI. According to Ephont Mon's story in Tales from Jabba's Palace Jabba was once very strong and fast. Years of spice (a Star Wars drug) abuse and poisioning attempts from his enemies erroded his body.

In the Return of the Jedi novelization, Jabba says "I was killing your kind when being a Jedi meant something" to Luke in the scene where Luke confronts him for the first time.

Rick McCallum has confirmed that Jabba the Hutt will be in the prequels. We can be fairly sure that Jabba will be hunting down Jedi in Episode III.

Finally, Lucasfilm registered the domain name www.jabba.net

Jabba will be saluted by all the contestants of the Pod Race.