- Disable SSID broadcast. Router still remains discoverable but not by general users. Causes intermittent problems on Mac OS X but not Vista
UPDATE: Windows machines expose the SSID when they connect, so Microsoft suggests that the SSID broadcast is kept enabled and encryption turned on [here].
- Enable MAC address filtering. MAC addresses can still be spoofed, but not by general users.
- Use WPA or WPA2 rather than WEP. Vista and Mac OS X support WPA2
From practically networked.