Demonstrating how to set up a RunspacePool with access to module commands, and shared access to .NET objects.

Runspace1.ps1

# $arrayList is the object I want to share across runspaces.

$arrayList = New-Object System.Collections.ArrayList

$sessionstate = [System.Management.Automation.Runspaces.InitialSessionState]::CreateDefault()

# Calling ImportPSModule("PSThreading") requires that the module be installed on the PSModulePath.  The
# method can also accept a file system path directly to a psd1, psm1 or dll file, such as
# $sessionState.ImportPSModule("$pwd\PSThreading.psm1")

$sessionstate.ImportPSModule("PSThreading")

# Sharing variables this way requires the creation of SessionStateVariableEntry objects.  The third argument to
# the constructor of this type is a "Description" field, but appears to be optional.  I've passed in both
# $null and [NullString]::Value for the third argument, without encountering any errors.

$sessionstate.Variables.Add(
    (New-Object System.Management.Automation.Runspaces.SessionStateVariableEntry('arrayList', $arrayList, $null))
)

$runspacepool = [runspacefactory]::CreateRunspacePool(1, 2, $sessionstate, $Host)
$runspacepool.Open()

# Now, the runspace pool is ready for use by PowerShell objects that will have access to my $arrayList variable
# and the Lock-Object function