Jazz is a very challenging form of music to play - many musicians have described it as a life-long quest in which you never stop learning. I found it not only challenging to play from a technical point of view, necessitating excellent sweep picking techniques, but also from a music theory perspective. It is one thing to learn the scales and arpeggios and quite another to be able to use them to improvise over a chord progression. In any case, I never got very far in my studies and don’t consider myself much of a Jazz musician.
However, I’d like to change this :-). My technique is still pretty good. What I feel I need is some concerted effort to learn chord progressions and practise improvisation. Jazz music has a large number of ’standard’ tunes which are played by just about everyone. They essentially consist of chord progressions which everybody knows, in various keys, and then the musicians solo over them using scales and arpeggios. One of the definitive collections of Jazz standards is the Charlie Parker Omnibook. Unfortunately, my copy of this book is somewhere unknown at this point. I don’t much feel like buying another copy just now, so I have been investigating online Jazz resources. I found a site, www.realbooks.us which provides access to hundreds of charts of Jazz standards online, with the ability to transpose them into various different keys dynamically. While I’m somewhat dubious of the legality of this website, it is certainly useful to the aspiring Jazz musician.
I’ve also been searching for online Jazz guitar lessons. Basically I’m looking for scales and arpeggios, and ideas for tunes to work on - along with recommended recordings. I found a few useful tidbits on freeguitarvideos.com which come complete with video lessons. However, this site seems geared toward whetting your appetite in order to sell you guitar education products rather than teaching you Jazz guitar per se. I also came across Jazz Guitar Online which has more content but still has a commercial vibe. There are a multitude of such sites on the Internet and I have yet to find any which are truly great. I will do some more sifting and post any gems I find.
Finally, I have been toying with a software package called Band in a box. Essentially, you feed it chord progressions and it generates an accompaniement in one of a huge variety of styles. Its output is reasonable from a practise perspective, but definitely has that cheesy 80s synthesizer feel. The interface is a bit clunky and amateur looking. However, I think it could be useful for practising improvsation. Simply input a standard, and play along with it. I think this could work well as an exercise. One last thing - the ‘Jazzy’ patch on my Korg PX4 makes my feeble efforts sound pretty damn good 
