I was recently asked about Sharepoint and Exchange integration (2003 on each).  I decided to document a few that I knew of

1.  Link to Outlook
This is a button on contacts or events lists that lets Outlook 2003 add a pst file named Sharepoint Folders and it links to the data on the site.  It’s read-only, but you could make the home page for that PST be the Sharepoint site for easier viewing.  The link to outlook feature seems more to me to be where someone can public a calendar, but not want too much collaboration.  For example, a holiday schedule, company meeting schedule, etc, can be made available for people to be able to view from Outlook without having to go to a web browser.  Another nice thing about OL2K3 is that you can compare these calendars with others side by side.

2. Searching Public Folders 
With SPS you can index Exchange’s public folders with the search engine so that all that precious public folder content is searchable.  You’ll want to look at content sources and indexing in Sharepoint administration.

3.  Displaying Public Folders in a web part.
Since exchange web-enables public folders, you can create a web part that displays that content.  IE, http://exchangeserver/Public/IT/Helpdesk will display the IT/Helpdesk public folder via OWA.  So you add the Page Viewer web part to a page and point it at that URL.  See http://www.spsfaq.com/customising.asp?postid=668 for more info.  The key here is to add ?cmd=contents to the end of the url if you don’t want the navigator pane on the left.

4. Smart web parts (can't remember where these are in 2003)
Some of the web parts that come with SPS allow you to add a web part to a page that actually takes the users outlook info (calendar, inbox, contacts, tasks) and put them into the page.  

If you have more, go ahead and let me know.