I would like to add recurring monthly membership fees to the WP E-Commerce plugin. Also I would like this plugin to give away a free gift/product on sign up with 10% off existing products. This one time sign up feature would also need to allow for a (one time?) free shipping on all products.
WP E-Commerce Plugin With Membership
S2Member is a great plugin for membership. It will let you do things like Platinum, Gold and Silver membership levels even. You will need to create a custom function in order to give a free product on sign up, but that should be some fairly basic PHP work. eShop is probably the best plugin for ecommerce I know of. The answer really is that you will need a couple plugins plus some custom coding to get it working the way you want it.
I feel like this question is extremely general and a bit inappropriate for this section, but I’d suggest looking at various WP E-Commerce plugins that you can customize to get the functionality you need.
Try taking a look at this one, for example.