I could be wrong, but I think the major carriers also have prepaid plans if you dig a little deeper (they just don't always advertise it since they want your $$$), and these plans don't have subsidies built-in. There's no contract, and you buy the phone outright. I don't think they have family plan options though, which is why I personally went with Ting (a prepaid carrier that uses the Sprint network) since they allow family members to pool minutes, texts, and data. But I'm pretty sure that even if you stay with the main four carriers, prepaid (and thus unsubsidized) is still an option.
Edit: For example, it looks like Verizon charges $60 a month for 2 gigs of data and unlimited calling and texting for both prepaid and postpaid plans, but with a subsidized postpaid plan, there's an additional $40/month "line-access fee" per phone (i.e., subsidy). Over 2 years that works out to be $960 extra. If you paid $200 upfront for the $650 iPhone, that leaves $450 left unpaid. So over two years you contribute $450 toward the phone itself, and $510 towards interest. So it seems even staying with Verizon proper, you save a lot by going prepaid.
Verizon prepaid:
http://www.verizonwireless.com/prepaid
Verizon subsidized:
http://www.verizonwireless.com/wcms/consumer/shop/share-everything.html
Note: They don't seem to offer the iPhone through Verizon as prepaid, but you can still BRING a Verizon iPhone (like one bought off of eBay, etc.) and activate it on a prepaid Verizon plan. But honestly, it still seems like too much hassle. I'd urge anyone who wants to save money by buying their phone upfront to either stick with T-Mobile/AT&T and buy the unlocked iPhone straight from Apple, or to just go with another prepaid carrier that offers the iPhone.