A month or so ago, I worked up an Excel spreadsheet to help me calculate XP earned by the party after a game session. I shared it over at the Troll Lord forums and folks seem to be digging it. Figured I'd share it here as well:
C&C XP Calculation Sheet
All you do is enter in the various XP info for critters slain (base XP + XP per HP), gold value for treasure, and any kind of story award you dished out. Then enter in the number of characters and, ta-da, XP for the session for each character involved.
I keep a separate Excel file for each session just in case I need to see what was dished out before. You could also just keep each session in the same file, but on a new sheet.