Being a victim of stalking is extremely scary and dangerous that unfortunately many experience. Below are some resources that may help you determine if you are being stalked, how to protect yourself, and the psychological effects of stalking.
Wikipedia Page on Stalking
Stalking behaviors, Definitions, Resources and Additional Links
A support community for anyone who has experienced sexual harassment
An Abuse, Rape and Domestic Violence Aid and Resource Collection – Stalking
Stalking Handbook (.PDF download – free)