(Working against me is the fact that in our group we play from charts and it's acceptable to do so, but I want to lose the charts and grow in this area.)
I tend to think of Weaning Myself Off The Chart as a slightly different process than Memorizing The Tune ...and in some ways it's a harder process.
But one of the techniques that's really helped me with the former is visualizing the chart in my mind. You don't need a photographic memory (though I'm sure that would be a big help!), you just need to "see" the salient passages that are the places where, when reading, you found yourself locked to the page.
If you can remember "ah-ha, we're about to come upon that two measure phrase that was in the lower right corner just before the page turn" it becomes a reference point as you play through the virtual chart in your head. Eventually you string enough of those reference points together that you realize you know the entire chart.
