<< You mean scaning from outside. the only way is to e-mail your isp and ask them to block that IP range. Other than that, your stuck with 'em. I get scanned about every 6-7 minutes. >>
You would basically have to block 90% of the ips out there. And no isp will do this for a consumer line (that Im aware of). So unplugging the network cable is the only real way to stop them. Keeping your software up to date, not using exploit prone software, being intelligent about downloaded files, not ignorantly setting up server software, and using antivirus and firewall programs will help you sleep at night.