SharePoint has a strange way of organizing new sites. Typically new sites are added at a URL such as servername/sites/sitename. This is the default setup, and if you want to allow users to create sites then they will all follow this format. The problem is that servername/sites is not a site itself. This can be confusing and annoying. It is possible to make a top level site like this by following these steps:
In Windows SharePoint Services Central Administration go to
Virtual Server Configuration / Create a top-level Web site
In the Virtual Server List, Click on the server name
On the Create Top-level Web Site page, under Web Site Address, click on the link that appears in the sentence "To add a new URL Path go to the Define Managed Paths page".
On the Define Managed Paths page, scroll to the bottom under Add a New Path
Path: Type in the name for this top level site. If you want the final URL to be "servername/portals", then type in "portals".
Type: Choose "Included path"
Type: Choose Explicit inclusion
This adds your new path (in this case "portals") to the list of Included Paths.
Go back up to Windows SharePoint Services Central Administration by clicking the WSS quick link in the left column
Go back to Virtual Server Configuration / Create a top-level Web site
Click the server name again in the Virtual Server List
This time in the Web Site Addresses section, choose "Create site at this URL:"
URL path = choose the path you just set up (example: "portals")
Fill in the Site Collection Owner, Secondary Owner, Quota Template and Site Language fields as needed, and click OK
Your new top level site has been created. You are given a link where you can go to the site and choose a template. You can access the site via the url servername/sitename (example: servername/portals)
There are a few things to keep in mind when setting up sites like this:
Microsoft's instructions warn: "Note: Web server performance declines lineraly with the number of inclusions and exclusions. You can minimize the performance impact by using wildcard inclusions rather than many explicit inclusions, and by putting as many excluded applications under the same excluded path as possible."
The list of inclusions also gets unwieldy after too many additions, as it doesn't sort in alphabetical order
Also, if you are on the main SharePoint site, and you choose "Sites" in the top menu bar, and then "Create Site" in the Actions list in the left hand quick link bar, you will only be allowed to create sites under paths created with Wildcard inclusions, such as the default "sites". You won't see paths created with Explicit inclusions. This is fairly annoying, as paths created with Wildcard inclusion are not sites themselves. They only have sites under them, so servername/sites is not a site, while servername/sites/sitename is a site.
To create subsites to a new Explicit inclusion site, simply go to that site (servername/portals), choose Create in the top menu, and then choose Sites and Workspaces.