The jQuery online docs are really good -- especially for online documentation. But they aren't exactly a tutorial that you can read through (sort of like trying to learn English by reading the dictionary).
I don't know of any thorough tutorials available online. But there are lots of blog posts you can search for that have mini-explanations of performing certain tasks.
Chapter 1 of jQuery in Action is a free download available here. It should at least give you a good overview of jQuery.