Ed Friedland's book. It gives you a basic outline of how to walk, with an example (in notation, 2 skills for the price of one) and then a progression for you to apply the concept to. The audio examples all have a bass line, but you can take the bass out of the mix and just jam your own line. You can also transcribe Ed's line for a bit of extra ear training if you like.
I like this book because it isn't just a book full of basslines, it describes a concept, displays the concept and then lets you apply concept without any sort of visual crutch. You actually are forced to learn how to play, rather than just read someone elses line.