Shopp's base installation supports physical and digital products as well as subscriptions with recurring fees. Customers can pay using PayPal, Google Checkout, 2Checkout or offline (such as checks or money orders).
If your store needs are modest and you don't require customer and inventory tracking, shipping fee calculators or digital product sales, something really basic such as WordPress Simple PayPal Shopping Cart will do the job. But for a more rigorous and robust e-commerce tool that works well and has excellent customer support, I'd recommend Shopp.
WPtouch can also be configured to replace the default WordPress theme on some devices (such as iPhones) but not others ( iPads), or can add a "1st visit mobile users will see desktop theme" option, which adds a link to the bottom of your page where users can opt to activate the mobile view.
One downside to this approach to creating a mobile site is that WPtouch does not inherit the look and feel of your desktop site -- as a result, most sites that run WPtouch will look alike.
WPtouch is free; a premium version, WPtouch Pro, enables more options for a one-time fee of $49 to $199, depending on how many sites you'll use it with.
These ten plugins are just a sample of what WordPress can be made to do. It's a flexible CMS that scales well and has plenty of support -- no surprise, given the number of businesses, individuals and organizations whose websites are built on it.
Whatever plugins you use, be sure to keep them and WordPress itself updated to the latest versions -- not just to get the latest and greatest features, but to ensure compatibility and to remain secure as patches are deployed. A site's success depends on an attentive and dedicated administrator -- and the above plugins can give you the tools you need to do your job.