So one of the most interesting requests that has been emailed to me as of late is how to use Outlook to schedule clients. In this particular case, SBS 2003 and Outlook were used to schedule a photographers time to take pictures of clients coming in to have their family pictures taken. The problem this particular small business was having was the calls were coming in too quickly and free/busy wouldn't be as up-to-date and clients would get double booked.
Outlook 2003, and Exchange 2003, free/busy information is all published through public folders on the server, and each client has to go get the free/busy information, which happens on a schedule basis. Outlook 2007 against Exchange 2007 has an "instant" view of the data retrieved on the scheduling tab, so this problem will disappear with the release of SBS 2008.
... But it's 2006 (at least for 11 more days)
KB Article 197088, expains how to speed up replication of Outlook 2003 clients to the server to make things faster than every 15 minutes (Which is the default).
In addition to speeding up the process, you may want to reference KB Article 291616 how to direct book resources, in this case a photographer (or even a camera).
The Exchange team did a blog post on how free/busy is generated which will explain more how things happen in the background.
Hope this helps with your resource scheduling, and no, Exchange 2007 will not be available for SBS 2003, you'll have to wait until SBS 2008.