In some sense, all scholarly accounts of the life of Jesus could be considered "secular," in that the methods employed are, at least ostensibly, not dependent on any religious conviction. In practice, it's a little more problematic, since few manage to find a Jesus they disagree with, and there is no history independent of bias.

A nice selection of various theories on the mission/character of the historical Jesus can be found on Peter Kirby's Early Christian Writings.

http://earlychristianwritings.com/theories.html

All of these positions, save "Jesus the Savior," have secular supporters, and even "Jesus the Savior," isn't as necessarily grounded in theology as one might suspect. Johnson, for example, thinks that the "Jesus of History" is inextricably linked to the "Christ of Faith," with the result being that you accept the Jesus of the New Testament as is or you don't, but you can't employ critical apparatus and expect to produce something historically meaningful. Even if one doesn't share his faith in the Jesus of the New Testament and church tradition, his criticisms of historical crit still have merit.

Each model has its own advantages and problems (and the methodological approach of almost all of them--with an emphasis on "criteria for authenticity"--is rapidly falling out of fashion), so if you're interested in the merit of any particular model it might be worth posting a more specific question.