To add some details about various versions.
Win 2008 Server is the Base server product from Microsoft. It Allows all basic services such as IIS, DNS, DHCP, Hyper-V, etc.
WHS, and SBS are both based on Win 2008 server.
WHS Has some feature limitations compared to that of 2008, but has a nice easy to use console. It also adds a pre-build Web access feature allowing for remote access of files and network desktops through a free
https://servername.homeserver.com address. This includes some nice media streaming features as well.
WHS also includes a network backup utility using Data De-duplication allowing for bare metal backups of your local PC's.
SBS comes in two flavors. Standard and Essentials.
Essentials is very similar to WHS. All WHS features are available with the exception of the media streaming. SBS Essentials does add the ability to join a domain.
SBS standard is a much more sophisticated package over essentials. It offers the same web interface, but also adds Sharepoint, Exchange, Web Mail, DNS, DHCP, VPN and is your Domain server for your network. All out of the box. What it doesn't have are any native media streaming or built in back up solutions similar to WHS or Essentials.
I use SBS Standard. I also configured Hyper-V on this machine to run WHS for backups of local PC's.