The Administrator guide lists all the OOTB ones:

The value must be in the form name#configuration. If you do not specify the
configuration, configuration 0 is the default (for example, STS#0). The list  of
available templates  can be customized to include templates you create.

Values available in a default installation include:

STS#0 (Team Site)

STS#1 (Blank Site)

STS#2 (Document Workspace)

MPS#0 (Basic Meeting Workspace)

MPS#1 (Blank Meeting Workspace)

MPS#2 (Decision Meeting Workspace)

MPS#3 (Social Meeting Workspace)

MPS#4 (Multipage Meeting Workspace)

Note If you added a template to the central template gallery, you must specify
the template name as _GLOBAL_#number, where number refers to the template ID.

Dim web As spWeb
web = SPControl.GetContextWeb(System.Web.HttpContext.Current)
Dim site  As New spSite(web.Site.Url.ToString)
Dim spWebTemplates As SPWebTemplateCollection =
spSite.GetWebTemplates(System.Convert.ToUInt32 (web.Locale.LCID))

This will give you all the site definitions/templates available on the
top level site.
The web.Locale.LCID is the LCID of the site.