Derren Brown has some great uses for pickpocketing in his latest book "Absolute magic".
They generally create effects which do not look like picking pockets has taken place, although in saying this, it is only a small chapter, but very thought provoking nonetheless.
As for material on pick pocketing, watchstealing material is endless, but there is not a whole lot of availible stuff on things like belt stealing, tie stealing ,ring stealing and so on, mainly due to the fact that in many hands it is dangerous.
In any case- try figuring out your own steals, and work out your own methods, as these will probably suite you more than what another person has wrote.
If in doubt, watch shows like bob arno on worlds greatest magic and similar things and look out for the steals, and watch how they're done.
A lot of it is the misdirection though, so dont get caught up in the methodology of it.