My profile.ps1 (and several related scripts)

cd.ps1

if ($GLOBAL:PWD -isnot [System.Management.Automation.PathInfo])
{
	$GLOBAL:PWD = get-location
}

if ($GLOBAL:CDHIST -isnot [System.Collections.ArrayList])
{
	$GLOBAL:CDHIST = [System.Collections.Arraylist]::Repeat($PWD, 1)
}

$cwd = get-location
$count = $GLOBAL:CDHIST.count

if ($args.length -eq 0) 
{
	set-location $HOME 
	$GLOBAL:PWD = get-location
	$GLOBAL:CDHIST.Remove($GLOBAL:PWD)
	if ($GLOBAL:CDHIST[0] -ne $GLOBAL:PWD) 
	{
		$GLOBAL:CDHIST.Insert(0,$GLOBAL:PWD) 
	}
}
elseif ($args[0] -like "-[0-9]*") 
{
	$num = $args[0].Replace("-","")
	$GLOBAL:PWD = $GLOBAL:CDHIST[$num]
	set-location $GLOBAL:PWD
	$GLOBAL:CDHIST.RemoveAt($num)
	$GLOBAL:CDHIST.Insert(0,$GLOBAL:PWD) 
}
elseif ($args[0] -eq "-l") 
{
	$start = [System.Math]::Max(0, $count - 50)
	
	for ($i = 0; $i -lt $count; $i++) 
	{
		"{0,6}  {1}" -f $i, $GLOBAL:CDHIST[$i].ToString().Replace("Microsoft.PowerShell.Core\FileSystem::","")
	}
}
elseif ($args[0] -eq "-") 
{ 
	if ($GLOBAL:CDHIST.count -gt 1)
	{
		$t = $CDHIST[0]
		$CDHIST[0] = $CDHIST[1]
		$CDHIST[1] = $t
		set-location $GLOBAL:CDHIST[0]
		$GLOBAL:PWD = get-location
	}
}
else 
{
	set-location "$args"
	$GLOBAL:PWD = get-location

	for ($i = $count - 1; $i -ge 0; $i--)
	{
		if ($GLOBAL:PWD.Path -eq $GLOBAL:CDHIST[$i])
		{
			$GLOBAL:CDHIST.RemoveAt($i)
		}
	}

	$GLOBAL:CDHIST.Insert($GLOBAL:CDHIST.count, $GLOBAL:PWD)
}

$GLOBAL:PWD = get-location

get-isadmin.ps1

$windowsIdentity = [System.Security.Principal.WindowsIdentity]::GetCurrent()
$windowsPrincipal = new-object 'System.Security.Principal.WindowsPrincipal' $windowsIdentity

return $windowsPrincipal.IsInRole("Administrators")

get-title.ps1

$host.UI.RawUI.WindowTitle

My.Types.ps1xml

<Types>
    <Type>
        <Name>System.String</Name>
        <Members>
            <ScriptProperty>
                <Name>ToBase64</Name>
                <GetScriptBlock>
                 [System.Convert]::ToBase64String([System.Text.Encoding]::Unicode.GetBytes($this))
                </GetScriptBlock>
            </ScriptProperty>
            <ScriptProperty>
                <Name>FromBase64</Name>
                <GetScriptBlock>
                 [System.Text.Encoding]::Unicode.GetString([System.Convert]::FromBase64String($this))
                </GetScriptBlock>
            </ScriptProperty>
        </Members>
    </Type>
</Types>

profile.ps1

# Sometimes home doesn't get properly set for pre-Vista LUA-style elevated admins

if ($home -eq "") {
    remove-item -force variable:\home
    $home = (get-content env:\USERPROFILE)
    (get-psprovider 'FileSystem').Home = $home
}
set-content env:\HOME $home

# Keep the existing window title

$windowTitle = (get-title).Trim()

if ($windowTitle.StartsWith("Administrator:")) {
    $windowTitle = $windowTitle.Substring(14).Trim()
}

# Posh-Git overrides

$GitPromptSettings.AfterBackgroundColor = "DarkRed"
$GitPromptSettings.BeforeBackgroundColor = "DarkRed"
$GitPromptSettings.BeforeIndexBackgroundColor = "DarkRed"
$GitPromptSettings.BranchBackgroundColor = "DarkRed"
$GitPromptSettings.BranchAheadBackgroundColor = "DarkRed"
$GitPromptSettings.BranchBehindBackgroundColor = "DarkRed"
$GitPromptSettings.BranchBehindAndAheadBackgroundColor = "DarkRed"
$GitPromptSettings.DelimBackgroundColor = "DarkRed"
$GitPromptSettings.IndexBackgroundColor = "DarkRed"
$GitPromptSettings.WorkingBackgroundColor = "DarkRed"
$GitPromptSettings.UntrackedBackgroundColor = "DarkRed"

$GitPromptSettings.AfterForegroundColor = $Host.UI.RawUI.ForegroundColor
$GitPromptSettings.BeforeForegroundColor = $Host.UI.RawUI.ForegroundColor
$GitPromptSettings.BeforeIndexForegroundColor = "Green"
$GitPromptSettings.BranchForegroundColor = "White"
$GitPromptSettings.IndexForegroundColor = "Green"
$GitPromptSettings.WorkingForegroundColor = "Cyan"
$GitPromptSettings.UntrackedForegroundColor = "Cyan"

$GitPromptSettings.AfterText = " "
$GitPromptSettings.BeforeText = " "
$GitPromptSettings.ShowStatusWhenZero = $false

# Type overrides (starters compliments of Scott Hanselman)

Update-TypeData (join-path $scripts "My.Types.ps1xml")

# Remove default things we don't want

if (test-path alias:\clear)           { remove-item -force alias:\clear }              # We override with clear.ps1
if (test-path alias:\ri)              { remove-item -force alias:\ri }                 # ri conflicts with Ruby
if (test-path alias:\cd)              { remove-item -force alias:\cd }                 # We override with cd.ps1
if (test-path alias:\chdir)           { remove-item -force alias:\chdir }              # We override with an alias to cd.ps1
if (test-path alias:\md)              { remove-item -force alias:\md }                 # We override with md.ps1
if (test-path alias:\sc)              { remove-item -force alias:\sc }                 # Conflicts with \Windows\System32\sc.exe
if (test-path function:\md)           { remove-item -force function:\md }              # We override with md.ps1
if (test-path function:\mkdir)        { remove-item -force function:\mkdir }           # We override with an alias to md.ps1
if (test-path function:\prompt)       { remove-item -force function:\prompt }          # We override with prompt.ps1

# Aliases/functions

set-alias grep   select-string
set-alias wide   format-wide
set-alias whoami get-username
set-alias chdir  cd
set-alias mkdir  md

set-content function:\mklink "cmd /c mklink `$args"

# Development overrides

set-content env:\TERM "msys"    # To shut up Git 1.7.10+

    if (test-path "C:\Dev\bin\Startup.ps1") { . C:\Dev\bin\Startup.ps1 }
elseif (test-path "D:\Dev\bin\Startup.ps1") { . D:\Dev\bin\Startup.ps1 }
elseif (test-path "E:\Dev\bin\Startup.ps1") { . E:\Dev\bin\Startup.ps1 }

prompt.ps1

$nextId = (get-history -count 1).Id + 1;
$currentPath = (get-location).Path.replace($home, "~")
$idx = $currentPath.IndexOf("::")
if ($idx -gt -1) { $currentPath = $currentPath.Substring($idx + 2) }

$windowsIdentity = [System.Security.Principal.WindowsIdentity]::GetCurrent()
$windowsPrincipal = new-object 'System.Security.Principal.WindowsPrincipal' $windowsIdentity
$title = $currentPath

if ($windowTitle -ne $null)
{
    $title = ($title + "  »  " + $windowTitle)
}

if ($psISE)
{
    $color = "Black";
}
elseif ($windowsPrincipal.IsInRole("Administrators") -eq 1)
{
    $color = "Yellow";
}
else
{
    $color = "Green";
}

Write-HgStatus (Get-HgStatus)
Write-GitStatus (Get-GitStatus)

write-host (" [" + $nextId + "]") -NoNewLine -ForegroundColor $color
if ((get-location -stack).Count -gt 0) { write-host ("+" * ((get-location -stack).Count)) -NoNewLine -ForegroundColor Cyan }

set-title $title
return " "

set-title.ps1

$host.UI.RawUI.WindowTitle = $args[0]

FYI, newer versions of posh-git and posh-hg provide a single Write-VcsStatus so you don't have to write each.