Earlier this month, CNET editor Josh Lowensohn posted about how Apple was reportedlywith the glass back on the iPhone 4, which was proving to be less durable than some had hoped. Now several sites are detailing how you can replace the glass back of your iPhone 4 with a metal one.
Removing the back--or "rear panel" as Apple calls it--is pretty simple (see ifixit.com's tutorial). And in just a few minutes you can swap in an inexpensive metal back for $12.99 from Hong Kong. Other backs are available, but Unpluggd says this is one of the few flat backs that's nicely beveled. (In the future, we expect to see many more backs hit the market).
Of course, Apple does have some strict rules about messing with your iPhone and voiding the warranty, so you may want to think twice about changing the rear panel and just get a case. We also don't know how a metal back would affect reception, so let us know if you've had any experience with one of these guys.