Wireframes
Wireframes, also known as SSD’s, can be very useful for some projects. My experience is that for most projects they’re not very necessary.
Wireframes are not a strict deliverable type that can fit any design project. Each project is different, each client is different. One way I look at wireframes is that they’re just a part of a design and fit somewhere in between a thumbnail sketch and a full blown production mock-up. Sometimes you just go from drawing to CSS and JavaScript. Wireframes be damned.