I'm also in the process of evaluating Corporate Time. I quite like it. I've got the actual calendar server running on a Sun, the web interface running on Linux, and it integrates nicely with my Cyrus IMAP server. The Outlook connector fakes out Windows users, but it also provides a web interface, and a native Motif client for UNIX users. This allows EVERYONE in the company to participate, as opposed to only Windows users.
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I'm also in the process of evaluating Corporate Time. I quite like it. I've got the actual calendar server running on a Sun, the web interface running on Linux, and it integrates nicely with my Cyrus IMAP server. The Outlook connector fakes out Windows users, but it also provides a web interface, and a native Motif client for UNIX users. This allows EVERYONE in the company to participate, as opposed to only Windows users.