The "PCI BUS" (your sound cards, network cards, hard drives and possibly your video cards) all sit on the frontside bus. When you overclock the CPU by changing the frontside bus speed you overclock all of those. When you changed the frontside bus speed you also overclock the ram as Thermal said.
The newer VIA Boards - boards using the VIA chipset rather than Intel's BX chipset - allow you to separately set the clock speed of your RAM. The settings are +/-33 MHz added to the PCI BUS speed. This allows you to clock your RAM up or down in relation to your FSB speed.