XLnotes add-in for Excel lets you to create notes for the cells, which
contain full-featured Word documents, web pages and attachments. XLnotes
turns Excel into a free form notetaking app

With XLnotes you can do following:

* create text notes
* save web pages and bookmarks to notes
* attach files to notes
* import and export notes to cells, comments and files
* search in notes
* merge and copy notes

After you install XLnotes, a notes tab will appear on the ribbon (in Excel
2007 and 2010) or in the menu (in Excel 2003). Adding notes is simple:
select a cell, where you want to create a note and click on the note button,
picking from three note types: Text note, Web page, and Attachments.