JumpChart for content, HTML and CSS for the grid, and JQuery and JQueryUI and PolyPage for the interaction. Add those pieces together. For the CSS, you should already have base stylesheets that get used as the foundation for custom frontend development, so those can be used; I would only use a framework if you are comfortable developing the final product on it.
I would rarely divide the task of building a website to have a specific step called 'wireframing'. The process itself, I think, is way more holistic. Although it doesn't require doing designs or the backend, prototyping and final development often require the same tools. The goal and main benefit is the reusability of assets. You can do your wireframes in Photoshop, if you're planning to use Photoshop heavily in the design phase. In general, your prototype evolves into your final product, especially if you keep it under version control with something like Subversion.