Normally the first question I get asked after I tell people that they can run Sharepoint v3 on a Windows Small Business Server 2003 is whether it will work through Remote Web Workplace. Problem is that, by default you must install Sharepoint v3 on Small Business Server 2003 in parallel to existing Sharepoint v2 that comes with Small Business Server 2003 (in place upgrades break things!). Now, Sharepoint v2 is known as http://companyweb to users within a Small Business Server 2003 network. So to work with Remote Web Workplace you would need to have http://companyweb point to the new Sharepoint v3 site installed in parallel on the Small Business Server 2003.
Is this possible? It certainly is. You basically need to do some swapping of DNS records and extending of Sharepoint virtual servers (in both v2 and v3). However, the bottom line is that you can get a Sharepoint v3 site to appear in Remote Web Workplace. Buuuuut, the question is that this certainly would be "non-standard" and unsupported by Microsoft. There is also a good chance that any updates that come out in future may have a problem because they are expect to see Sharepoint v2 at http://companyweb not Sharepoint v3. However, if you REALLY, REALLY want to do it, then it can be done in a way that allows you to roll back if necessary when updates come out.
So how is it done? If you want to know then I suggest you subscribe to my Windows Sharepoint Operations Guide at http://wssops.saturnalliance.com.au. In here I have documented the steps as well as providing screen shots of just about every step to make it nice and easy. That section alone is currently over 50 pages and growing but relies on other parts of the guide to illustrate the process, which I do not plan to replicate here. I should also mention the fact that I have spent quite a few hours testing and documenting the whole process.
If you are planning on working with Windows Sharepoint especially on Windows Small Business 2003 then, I believe, my Windows Sharepoint Operations Guide represents a very small investment for the time savings it is going to give you. A really good example of that is getting Sharepoint v3 working as http://companyweb on a Small Business Server 2003.
The good thing is that existing Windows Sharepoint Operations Guide subscribers will get all this information as part of their next subscription update!