No and no I'm afraid - the SharePoint/Outlook integration requires PSTs
in both 2003 and 2007.

There is a way to display the team  calendar in Outlook, but it won't be
integrated or synchronized in any way. Simply add the URL of the team
calendar as the home page for a new folder in Outlook and show the home page
by default. It will at least allow you to look at the calendar  without
opening up a separate browser window.

Check out the following (from the Outlook 2007 Group Policy template) --
we use this to keep users  from creating  PSTs for email, while still
enabling SharePoint (and other apps) to use PSTs. PST are a bad idea as
a mail store -- they're often not on servers, and therefore often not
managed/backed up -- but we're ok with using them in this manner since
the data in the PST is sync'd to SharePoint:
Prevent users from adding PSTs to Outlook profiles and/or prevent using
Sharing-Exclusive PSTs Setting Path: user  Configuration/Administrative
Templates/Microsoft Office Outlook 2007/Miscellaneous/PST Settings
Explanation By default, users can add PSTs to their Outlook profiles and
can use Sharing-Exclusive PSTs for storing SharePoint Lists and Internet
Calendars. You can use this setting to limit users' ability to store
mail in a decentralized fashion. You can block the use of PSTs
completely, but be aware that blocking all PSTs disables Outlook
features such as SharePoint Lists and Internet Calendar.

If instead you allow only Sharing-Exclusive PSTs to be added to user
profiles, PST usage is still limited but the Outlook features that rely
on special PSTs are not disabled. The setting that allows
Sharing-Exclusive PSTs to be added blocks users from creating new
folders in the Sharing-Exclusive PST; copying existing mail folders from
their default store to the PST; and copying individual mail items to the
root of the PST.