How do you get your ex-husband to leave you alone?

Ask for a Restraining Order to be filed against him. Prepare to back up your claim when talking with Law Enforcement. Make sure you have a good attorney. If necessary, call a local battered women's shelter and ask if any space is available for a woman with kids (if you have kids) or without (if you do not). Stalking is illegal, but enforcement is only in recent years starting to truly take it seriously. Which is good, as some spouse-turned-stalker cases end up as homicides. Protect yourself, Sister!
Date a biker =)