Simple function that leverages the Crypto API to generate truly random passwords.

New-Password.ps1

Function New-Password
{
    <#
        .SYNOPSIS
            Create a new password
        .DESCRIPTION
            This function creates a password using the cryptographic Random Number Generator see the 
            MSDN link for more details.
        .PARAMETER Length
            An integer that defines how long the password should be
        .PARAMETER Count
            An integer that defines how many passwords to create
        .PARAMETER Strong
            A switch that if present will include special characters
        .EXAMPLE
            New-Password -Length 64 -Count 5 -Strong
            Password
            --------
            UkQfV)RHwcQ3a)s8Z#QwSCLxlI*y28kEPmcQUVM2HrACf@PxRJDLk4ffge#1m_8j
            XfAwZOh_lrzLE8NwkSTPs5#LNkW4uZ0Wm_ST5UzERqhY45)HBpN$_@@MxDeLiosW
            h(BN(y^Gip&pU$KJpAAajgopQyoSbCn41m53mc__wV@q$DY5a$iN&O0fnf9hvO1&
            tXkFwY_pe(VIFf$R2^bKyKy)D_H6q^Nz7MgSDylXrV2GIkyiFVnvfbd9KENFuHQz
            &6LPlWRB$#yqD@!IEuJ9JcMTKrsA_t(AbWRGTLx@2Fw__j08n(TGi6wgPE6XlLWg
            Description
            ===========
            This example creates 5 strong passwords that are 64 characters long
        .NOTES
            FunctionName : New-Password
            Created by   : jspatton
            Date Coded   : 05/01/2013 12:20:00
            The main portion of this code was lifted from Peter Provost's site, I modified it
            to handle varying length, and count.
        .LINK
            https://github.com/jeffpatton1971/mod-posh/wiki/ComputerManagement#New-Password
        .LINK
            http://www.peterprovost.org/blog/2007/06/22/Quick-n-Dirty-PowerShell-Password-Generator/
        .LINK
            http://msdn.microsoft.com/en-us/library/system.security.cryptography.rngcryptoserviceprovider.aspx
    #>
    [CmdletBinding()]
    Param
        (
        [int]$Length = 32,
        [int]$Count = 10,
        [switch]$Strong
        )
    Begin
    {
        switch ($Strong)
        {
            $true
            {
                [string]$Characters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890 !@#$%^&*()_+{}|[]\:;'<>?,./`~"
                }
            $false
            {
                [string]$Characters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890"
                }
            }
        $Passwords = @()
        }
    Process
    {
        for ($Counter = 1;$Counter -le $Count; $Counter++)
        {
            $bytes = new-object "System.Byte[]" $Length
            $rnd = new-object System.Security.Cryptography.RNGCryptoServiceProvider
            $rnd.GetBytes($bytes)
            $result = ""
            for( $i=0; $i -lt $Length; $i++ )
            {
                $result += $Characters[ $bytes[$i] % $Characters.Length ]	
                }
            $Password = New-Object -TypeName PSobject -Property @{
                Password = $result
                }
            $Passwords += $Password
            }
        }
    End
    {
        Return $Passwords
        }
}

New-PasswordV2.ps1

Function New-Password
{
    Param
    (
        [int]$Length = 32,
        [int]$Count = 10,
        [switch]$Strong,
        [switch]$Readable
    )
    Begin
    {
        if($Strong -eq $true)
        {
            [string]$Characters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890 !@#$%^&*()_+{}|[]\:;'<>?,./`~"
        }
        else
        {
            if ($Readable -eq $true)
            {
                [string]$Characters = "abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ1234567890"
            }
            else
            {
                [string]$Characters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890"
            }
        }
        $Passwords = @()
    }
    Process
    {
        for ($Counter = 1;$Counter -le $Count; $Counter++)
        {
            $bytes = new-object "System.Byte[]" $Length
            $rnd = new-object System.Security.Cryptography.RNGCryptoServiceProvider
            $rnd.GetBytes($bytes)
            $result = ""
            for( $i=0; $i -lt $Length; $i++ )
            {
                $result += $Characters[ $bytes[$i] % $Characters.Length ]	
            }
            $Passwords += $result
        }
    }
    End
    {
        Return $Passwords
    }
}