Laura:
amazon's library of Linda's workouts is more extensive than Mary's site. What you might like to do tho' is buy the boxed sets from Mary because then you get even more bang for your buck. About 11 workouts in a boxed set, plenty to experiment with and see what you think, $25 for the set. Bargain!
Watch out though: the workouts currently being assembled and released by Linda in boxed sets and largely pre-released material. So, before you buy, look carefully at the contents listed. I have now twice made the mistake of rushing to buy single DVDs (and even then, there are at least 3 if not 4 workouts on each DVD) from amazon, only to then have Linda release them in a box set with 2 other series all together. It saves money to get the box set collections. She has another boxed set that will be released by Mary in the coming weeks too.
I would say that your best bet is to head to youtube and view Linda's workouts there and figure out what you need to and want to buy after reviewing clips/footage. She has more released than even JenGolf --the lovely lady and very helpful blogger, aka enabler! Jen we all love you!)-- has managed to review yet so you might find things that appeal to you that have not been mentioned by any of us yet.
Linda make sit all look terribly easy. But as Jen has said here: Linda will burn out every muscle! You think you are in great shape because you match Cathe's weights and beyond, but these micro-movements are no joke!
Clare