Vincent (no last name given) has designed a beautiful, extremely useful, feature-rich interface design framework for web designers who create their initial design mock-ups in Adobe Illustrator. And it’s free for personal or commercial use (credit link required).

The set includes:

GUI library – Hundreds of vector elements for interface design
Minimal UI icons set – 260 vector icons for Illustrator
Styles library – 200 styles to apply in Illustrator

I’d pay cash money for the color schemes alone: 330 swatches harmonized with graphic styles for backgrounds, typography and other GUI interface elements.

The back-link requirement may be a deal breaker in some situations. I’d happily use these GUI icons on a personal project, but I might refrain on a client project if it seemed awkward to include a widget credit on the site. (It all depends on the client.)

That possible caveat aside, this is an extraordinary set of widgets and gizmos many web designers will want to have in their tool kit.