Enter Syncing.net, which keeps all your Outlook data in sync across all your PCs. It also provides shared folders that are easily accessible from Windows Explorer. In short, it's a soup-to-nuts solution -- but not a free one. Check out the quick overview video before I hit you with the bad news:
Syncing.net works in all modern versions of Windows (2000 and later) and supports virtually every version of Outlook (2000 and later, including the Outlook 2010 beta).
The Home Edition costs $149.90, which includes licenses for three PCs. If you have more machines and/or want more advanced features, Syncing.net Professional Edition costs $119.90 per PC.
That may seem like a lot, but it's a drop in the bucket compared with deploying an Exchange server -- which is usually what's required for this kind of functionality.
What's more, you can test-drive Syncing.net for 30 days, complete with technical support. That should help you determine if this is a good solution for your business. Much as I'm not wild about the price tag, I do think Syncing.net will fill a need for a lot of users.