It is not possible with Outlook 2003.

Even the Outlook 2007 option requires those users to be able to handle .ost files.

For this reason in my upcoming WSS 3.0 book (Oct 2008) I suggest instead the use of Colligo Reader for users who want to off-line easily see data from a WSS 3.0 site.

Colligo Reader is free - the chargeable product Colligo Contributor (or some such name - I don't work for them!) allows them to update the sites off-line too which shouldn't be necessary.

Colligo is probably at www.colligo.com otherwise search on the name.

The sites look roughly as they do in the real thing.

(Warning: I've not used this myself for looking at the *contents* of documents in document libraries so you'll have to check this aspect but everything else I've tried has worked.

P.S. I should have said to be 100% clear that Colligo Reader is a product which needs to be installed on the Client PC(s). Nothing needs to be installed on the server. Once the initial site copy (where the user can select which lists he wants to see in the off-line copy) has been made, everything else happens through quick synchronization.