Deadbeat clients

Oh, if only I still had the FTP log-ins for this company’s website because I’d shut it down in a heart-beat.

This was the project:
Two Flash-based websites. I delivered both the completed sites in early August, invoiced the final amount with a due date of early September. Previous invoices have been paid but always severely late. This last one is now 3 months late and I’ve already sent them two notices. The last one had a due date of this week.

I’m guessing I wont’ see the check this week, so what do I do? Small claims court? Can I ask for me since I could have invested that money?