I have the EVO. There is HTC software to sync with Outlook, but not so reliable. I now use Google Calendar Sync, which syncs Outlook to phone via Gmail account, so don't even need to plug it in. Just install on your PC.
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After the comparison to putting dice on the mirror in my Ferrari, I did some poking around and found I can add a "corporate" account right out the box. I didn't configure it yet, but assume that's the reason it's not necessary. Now I really don't know if it does calendars though, so i'll let you know when I get around to tying it to my corporate mail.
If you have Microsoft Exchange - you'll be all set.
If you don't, and you want to sync with Outlook, you'll need to use Google Calendar Sync.
There are other 3rd party applications out there, but if you have Microsoft Exchange it won't be an issue.