A minor correction to Bert's post. SBS 2011 has 2 main versions. Standard and Essentials. With SBS 2008, there was Standard and Premium. The "equivalent" to SBS Essentials was Foundation Server.
Now, you can apply the premium add-on to either one. You can use the Premium Add-On with SBS Essentials as well if desired. The add-on is just Server 2008R2 and SQL Standard. (Bundling them together saves you a few hundred bucks and the CALs are cheaper too.) Which means you can get SQL Standard too if desired on Essentials.
SharePoint foundation can also be installed separately (which I demonstrated earlier on Windows 7). It's free. Obviously, it won't be the same as the tailored SBS 2011 Standard one, but still pretty good.
I probably love Exchange as much as Bert loves SharePoint. Having control over your own email server is awesome. SBS Standard is definitely worth the money. Most people don't care much about Exchange so they go with Essentials.