Zinio Digital Magazines is an online service where you can get subscriptions or download individual issues of magazines. The subscriptions are cheaper (since there isn't the cost of paper, etc), but the individual issues can be a few dollars more than what you would pay at the store. The subscriptions or issues you pay for can be download and read at a later time.
There isn't a huge selection, especially for things I'd want (Martha Stewart, etc), but there are common beauty magazines and of course, Yoga Journal.
If you're looking for a way to cut back on the amount of paper you use, this is a great way to do so. And if more people use Zinio, then you'll probably be seeing more magazines offered.