A good, if brief, overview here from Alan Bandy on Intertextuality. I think he limits intertextuality too much and fears the broadening of the category too much - but I would. On Tuesdays, Thursdays and Saturdays, I am Kristevan/Barthian through and through, on Mondays, Wednesdays and Fridays Genette has me, and on Sundays, I don't really care!
Alan also gives a good overview of Hays - I've been reading this over the summer. It's an interesting, if overly wordy, book. I'll try and review it on the blog asap.