The Office 2003 Service Pack 1 can be downloaded from the Office Update site. According to ActiveWin, new features include:
Calendar logging in Outlook
Access Wizard file updates are built into the main service pack
Performance improvements in Project Server
Org chart and printing fixes in Visio
Charting and function improvements in Excel
Improved Mail Merge capability with RTF docs in Word
Bug that could cause CAB files to be removed from the \MSOCache folder is fixed
Improved alert message for FileOpen failures caused by out of date Norton AntiVirus software
Security and stability fixes that have been addressed