How do I "blacklist" a wireless network on my Mac?
Remove it from the list of "Preferred Networks" and it will stop auto-connecting.


Go to "System Preferences" > "Networks" prefpane.
Choose "AirPort" (or "WiFi" on Lion) on the left.
Click the "Advanced" button.
In the resulting sheet, choose the "AirPort" (or "WiFi") tab. (It should be the leftmost.)
Select your neighbor's wifi network in the list and hit the "-" (minus) button.
Live with joy at never [auto-]connecting there again!