Google Docs is an online alternative to Microsoft Office applications. It includes word processing, presentation, spreadsheet, form, and drawing tools. All documents can be shared with other users to just view, or to collaborate.
This would be a fun resource for students for something like writing an article or book summary. They can write a very succinct "newspaper" article, save the resulting image, and then students can read summaries written by classmates.
I chose YouTube as a business education web 2.0 tool because many businesses use YouTube to launch alternate marketing campaigns. A recent example is Old Spice. The "Old Spice Guy" responded to messages that were submitted via Twitter. The result was both personal and entertaining.