Let's give a few of the the Internet How-to-Spy sites a view. It is a good education, especially if you want to know what to protect yourself against!
First Stop...
How to Spy Computers, Helping You Spying Computers (sic)
• Should you spy on your employees?
• Is a keylogger completely hidden?
• How can I spy on what my spouse is doing on our home computer?
• What Is a Keylogger?
• Why Should I Spy on My Home Computer?
• How to Spy a Computer and Receive Reports by Email
• 7 Keyloggers for Windows Vista
• Keylogger for Mac
• All-Spy Keylogger Tutorial
Second Stop - 14 Tools to Legally Spy On Your Competition
Third Stop - How to Spy on Your Competitors—Without the Guilt