Saturn

To run homebrew or ISOs on your Saturn you'll need a modchip.

Right now the only modchip that is currently in production is the v3 Universal one, which will work with any console.

There will also be a flash cart for the Sega Saturn, little is known about it so far though. Here's the official site:

http://www.sarooo.com/

There's also a swap trick, but it's been known to damage the console, so it's highly discouraged.

Reseller
http://www.segastyle.com/store/index.php?route=product/product&product_id=76