I'm not ashamed to admit that I love Safari. Unfortunately, not all web developers are hip to it, especially when it comes to Ajax-based web apps. In fact, I'd have trouble naming very many web-based, "WYSIWYG" editors, let alone full collaboration suites, that work well with Safari. That's why I was pleased to hear that the Leopard-loving folks at Zimbra, the open source messaging and collaboration suite, have announced expanded support for Mac users, including Safari compatibility. To the best of my knowledge (and according to their press release), this makes them the first major collaboration suite to support Safari.And the support, especially in the document editor, is good. It uses valid XHTML tags and CSS to create cross-browser compatibility. I think the feature I love the most right now is the full support for rich text pasting (and no font tags). If you're using Firefox, you get page previews, monetary conversions and more when hovering over different bits of information. These seem to be missing on Safari, but that could be on account of an odd setting in my configuration.
In addition to Safari support, Zimbra has also added support for CalDav, allowing iCal 3 to sync and share calendars through its server. And for the mobile set, they've added a mobile HTML client that makes the suite iPhone compatible. With the preexisting Zimbra Connector for iSync, Zimbra users can sync their email, address books and calendars to their iPhone.
You can catch Zimbra at Macworld in booth W-4348. Zimbra is available for free as the ZCS 5.0 Open Source Edition. They also offer a Network Edition with commercial support, educational discounts available. And for the curious, you can demo the suite online at their website.