In-cell Graphing
The guys from Juice Analytics have put together an interesting series on in cell graphing (parts 1, 2, & 3). This is a feature that is due in the upcoming version of Excel 2007, however the technique the Juice guys use works across all versions of Excel and is quite visually appealing too. Added bonus, I can confirm it works in OpenOffice.org, Gnumeric and even Google Spreadsheets (all to varying degrees).