One of the other handy features of the new conditional formatting tool in Excel 2007 is that it can handle date formatting. For example, if you have a worksheet with a series of dates in it you can highlight the dates that correspond to a period of time.
Choose Conditional Formatting > Highlight Cells Rules and choose the A Date Occurring option. You can then format cells using rules such as Yesterday, Today, in the last seven days, this month, next month, next week, etc.. When you do this cells containing dates which match this criteria will be coloured appropriately. Better still, when the date changes, the formatting on the worksheet will change accordingly.