Box shot has a free online tool that you can use to create 3D images of your ebooks, DVDs, CDs. It is one of the few online free creators that will do DVD and CDs. Most of the time you are limited to books, and electronic devices. See below the types that are available.
Check it out here: http://boxshot.com/3d-pack/
BoxShot also has a production level software that you can download and use on your computer. More info on that is here: http://bit.ly/BoxShotInfo
Adazing has a pretty good selection of 3D eBook cover styles available. The one ‘drawback’ to their free service is that you must provide an email to download your product. But you can always use a fake email address.
You can give it a test drive here: http://www.adazing.com/cover-mocks/
They have a “premium” module you can access here: http://www.adazing.com/cover-mocks-2/ Using the password: coverpro27
My eCover Maker:
Will need a free account, but you can always use an account specifically for spam if you are worried. I’ve never received a single email from their website.
You can get started here: http://www.myecovermaker.com/ecover-design