A few people have already used "Web 0.5" by back-construction from Web 2.0. Sean Coates used it derogatively of MySpace, but this O'Reilly blog post is more positive, suggesting Web 2.0 is a return to earlier Internet applications.
But if Web 2.0 was about interactivity and collaboration in a community context, Web 0.5 should have less of those - while still being part of the Web. So I prefer to use the term for web sites that don't support comments or other interaction, aren't dynamic, and could have existed in 1993 (a decade before the Web 2.0 conference).
I don't see this as negative - just as print books and ebooks coexist, there's no reason for web sites to all be embedded in social networks.