Prototyping Services

Shapeways

Pros

• Laser Sintered Stainless Steel
• Full Color
• Shapeway Shops You design it, they sell it for you
  

Cons

• No Laser Cutter
• Grouping parts for assemblys is problematic
• Can not currently ship fasteners with orders

Ponoko

Pros

• Laser Cutting
• Easy to use templates
• Leather!?
• Online Shops
• Can sell your design or finished product
• Seller can ship finished and assembled product to customers

Cons

• The interface is occasionally somewhat dis-intuitive
• Only flat things

Protomold

Pros

• Injection molded parts
• Sample

Cons

• Prices start at $1495
• Quotes are not instantaneous

First Cut

Pros

• Solid Plastic
• Aluminum

Cons

• More expensive than 3D Printing, prices start at $95

RedEye on Demand

Pros

• Best Price Guarantee
• Fast Delivery Times
• Resources

Cons

• $150 Minimum

QuickParts

Pros

• Wide range of processes
• Metal Casting
• Sheet Metal
• Samples
• Fast lead Times

Cons

• Cost
• Some quotes are not instant

While this quick roundup of prototyping services is obviously biased. I think most of these companies serve slightly different prototyping needs and may be more or less useful at different stages of making.

Any other suggestions?