"... it is our opinion that ODF, as standardized and licensed by ... (OASIS), is free of legal encumbrances that would prevent its use in free and open source software." -- Eben Moglen
Patrick has now released both the PPC and Intel versions of NeoOffice 2.0 for free download - that's OpenOffice.org for Mac delivered with ODF & without the need for X11 and with proper system integration. It's what I use in all my keynotes.
ODF or OpenDocument Format is an file format standard for office documents, developed by OASIS. ODF has been accepted by ISO as ISO 26300 International standard.
ODF is positioned as an open alternative to Microsoft’s proprietary Word and Spreadsheet file formats, and is supported by various parties including OpenOffice and Google Spreadsheet.