Zoho's got something new: Notebook. If you've used Microsoft's OneNote, you'll grok it pretty quickly. It's a content editing system that lets you create multiple sheets in one document; great for big, complex projects.
Storage of PDFs, files, images, links, and whole web pages. Automatic capture of citation information from web pages. Playlist-like library organization, including saved searches & tags. Integration with WordPress and MS Word. Interface in many languages.