Here are a few resources provided by state agencies that cover their specific implementations and safety information. Many of the links provide photos or video of local roundabouts.
To find listings of roundabouts in your state, you can visit our Modern Roundabouts Database.
Arizona Department of Transportation
Design Information Bulletin 80-01 (2001, pdf)
Florida Roundabout Guide(1998, pdf)
Maryland State Highway Administration (SHA) Roundabout Web Site
New York State DOT Roundabout Web Site
Oregon DOT Roundabout Web Site
Washington State DOT Roundabouts Web Site
Washington State DOT Highway Design Manual chapter on roundabouts (PDF)
Wisconsin DOT: Using a roundabout
Wisconsin DOT: Design Guidance (with links to PDF files)