Microsoft released the first update specifically for SBS 2008, information can be found in KB958715. The Officical SBS Blog also discusses the update. The update addressess two issues in the initial release of SBS 2008:

1. The Security Tab in the SBS console did not correctly report anti-virus status on connected workstations for some anti-virus programs. I’ve been experiencing this with Sophos Anti-virus, which we use with our client base. After installing the update, I can confirm that the anti-virus status is now correctly reported with Sophos Anti-virus on the workstations.
2. The Internet Address Wizard stops functioning when registering a domain name through GoDaddy.

The update is now available through Microsoft Update and should appear in the Update subtab of the Windows SBS Console. You can approve the update in the console and allow it to roll automatically through WSUS, or you can manually install the update as follows:

1. Open the Windows Update panel from the Start Menu.
2. Click the Check online for updates from Microsoft Update link in the panel.
3. When the check finishes, you should see at least one update available. Click the View available updates link to see all updates available.
4. Under Windows Small Business Server 2008, you should see the Update Rollup 1 for Small Business Server 2008 (KB958715) in the list and checked.
5. Click Install to install the update.

No restart is needed after the update installs, but you should close the SBS Console prior to installing the update.