[Today] The current date.
[Me] Current User of the site.
[Modified] Date item was last modified.
Filter Expression Examples:
[Modified]+7 A week after the last modification.
DATE(YEAR(Modified),MONTH(Modified),DAY(Modified)+5) 5 Days after the last modification.
Formulas and Functions:
http://office.microsoft.com/en-us/sharepointtechnology/CH100650061033.aspx
