Macbook Pro frequently experiences drops in WiFi connection with Linksys WAG120N
Do you have DHCP enabled? Your laptop might be loosing its connection to the router due to IP conflicts resulting from other devices on your network using the same IP address.
Try using different broadcast channels. I think the default Linksys channel is 6. I usually use 8 or 1.
How good is the signal strength? You might have to boost the antennas transmission signal.
Make sure someone like your neighbors are not running APs with the same SSID.
If you use signal encryption try using different key encryption WPA/WPA2-PSK(AES/TKIP).
and the obvious one, run software updates, just to make sure that there is no new firmware for the MacBook NIC.