Google tests a service called Cloudboard, an online clipboard that should make it easy to copy data between Gmail, Google Docs and other Google services. The service is not publicly available yet, but there are many references to it.
An internal feedback form (update: Google disabled the form) describes Cloudboard as a "server-side clipboard for Google Apps". Google provides an example of copying data from Google Spreadsheets to Google Docs: "if you copy a formatted cell range in Trix (cell border, colors, etc.) and then paste into Writely, it's transformed into a comparably-styled HTML table."
Google's feedback form includes many other examples: pasting excerpts from Google Spreadsheets to Gmail, copying multiple images from Picasa Web Albums, copying YouTube videos, copying an event and pasting it into Google Docs or Gmail, pasting copied items from Google Image Search, copying maps into Google Docs etc.
I've always thought that Google Notebook will be Google's web clipboard, but now that the service has been discontinued, Cloudboard will be the bridge between Google's services.