Update: Mike Walsh has had quite a post up on this topic for quite some time:
http://www.asaris-matrix.com/mvp-walsh/Lists/WSS%20FAQ/DispForm.aspx?ID=32
Amit Saxena posted the following helpful information to the Mindsharp sponsered Yahoo Group: http://groups.yahoo.com/group/sharepointdiscussions. I didn't validate Amit's assertions.
The following browsers can access a SharePoint Portal:
• Microsoft Internet Explorer 5.01, plus the latest
service pack
• Internet Explorer 5.5, plus the latest service pack
• Internet Explorer 6.0, plus the latest service pack
• Netscape Navigator 6.2 or later
• Netscape Navigator 6.2 for UNIX
• Internet Explorer 5.2 for Mac OS X, plus the latest
service pack
• Netscape Navigator 6.2 for Mac
Safari and Firefox work on a Mac too, but in most cases Safari does not render the page properly. Firefox works well in most of the time. Datasheet view is not available in any Mac based browser.