Exporting curves is one of the more compelling examples of the flexibility that 3D modeling programs offer. By exporting vectors, you can import them in to a wide array of programs to use for illustrations, machining, guides, etc. That is the great thing about vector data — you can use it anywhere!
To export curves in Rhino, select your curves, then go to “File”>”Export Selected”>and choose the Adobe Illustrator format (.AI). From there you can use the curves for whatever you might need them for.