At work I have an Excel spreadsheet that has GMT, PST, PDT conversions, and Julian (calendar) dates on it. I originally created it for use during satellite contact planning. I think I also have one for elapsed seconds over the course of the day (86400 seconds in a day).
I don't think it's updated for 2007, but I need to update it anyway. If anyone wants either of these, PM me your e-mail address and let me know which one(s) you want; I'll update the spreadsheet this week, and e-mail it out to you. It will be in Excel 2003, two sheets; one for Jan-Jun, one for Jul-Dec. 8.5x11 landscape, suitable for framing or putting in a document holder for reviewing both sides.
Matt