Creating a new Sharepoint Site Collection:

# SharePoint cmdlets
Add-PsSnapin Microsoft.SharePoint.PowerShell
# Templates
# Name                 Title                                    LocaleId   Custom
#     ----                 -----                                    --------   ------
# GLOBAL#0       Global template                       1033       False
# STS#0                Team Site                                 1033       False
# STS#1                Blank Site                                1033       False
# STS#2                Document Workspace             1033       False
# MPS#0               Basic Meeting Workspace       1033       False
# MPS#1               Blank Meeting Workspace      1033       False
# MPS#2               Decision Meeting Workspace  1033       False
# MPS#3               Social Meeting Workspace      1033       False
# MPS#4               Multipage Meeting Workspace 1033       False
# CENTRALADMIN#0       Central Admin Site    1033       False
# WIKI#0              Wiki Site                                   1033       False
# BLOG#0            Blog                                           1033       False
# SGS#0                Group Work Site                       1033       False
# TENANTADMIN#0        Tenant Admin Site      1033       False

# Languages
# Name                  Title
#     ----                  -----     
# German               1031
# English               1033
# French                1036
# Spanish               1034

# Set variables
$SiteCollectionName = "Homepage"
$SiteCollectionURL = "http://sharepoint.contoso.com"
$SiteCollectionTemplate = "STS#0"
$SiteCollectionLanguage = 1033
$SiteCollectionOwner = "contoso\UserName"

# Create a new Sharepoint Site Collection
New-SPSite -URL $SiteCollectionURL -OwnerAlias $SiteCollectionOwner -Language $SiteCollectionLanguage -Template $SiteCollectionTemplate -Name $SiteCollectionName