The following snippet gets the current directory whether or not it's run from a script or a PowerShell host. I put this at the top of nearly every script I write. Blogged as powerbit #9 here: http://powertoe.wordpress.com/2012/11/02/powerbits-9-set-the-current-directory-to-the-script-directory-or-the-current-directory-if-run-in-a-session/

currentdir

# http://powertoe.wordpress.com/2012/11/02/powerbits-9-set-the-current-directory-to-the-script-directory-or-the-current-directory-if-run-in-a-session/

$currdir = ''
if ($MyInvocation.MyCommand.Path) {
    $currdir = Split-Path $MyInvocation.MyCommand.Path
} else {
    $currdir = $pwd -replace '^\S+::',''
}