Fabrication

• Ponoko offers laser cutting of materials based on design templates, and a supporting market place to sell your designs. If you sign up for a Prime account, they will also source local materials and work with you.
• An article on Wired mentioned eMachineShop, which is a more traditional "upload your CAD files" prototyping shop.
• TechShop in San Francisco is a machine shop operated like a Health Club: monthly membership, access to all kinds of CNCs, laser cutters, vacuum formers...cool stuff!
• Shapeways offers 3D printing, using plastic materials.
• Materialise.com is another more technical service, like eMachineShop.

Customized Products

• Cafe Press allows you to upload your artwork and customize mugs, calendars, t-shirts...
• Zazzle is another such company.

Packaging

• Jewelboxing sells the materials to make awesome CD cases.

Book Publishing

• Blurb lets you upload and format your existing blog (if it's small enough) into book form, using digital Print on Demand technologies.
• Lulu also lets you upload and create a variety of books, using Print on Demand.

Fulfillment and Shipping

• Amazon Fulfillment
• Amplify