Squeaky brakes are usually caused either by dirty rims or by out-of-alignment brake pads. Don't oil the brake pads, as this will actually make the squeal louder and will significantly reduce your braking power.
You can clean your rims (where the brake pad contacts the rim) with soapy water and a brillo pad.
If the brake pad surface appears glazed, you may want to try lightly sanding it.
A good article on dual pivot brake adjustment can be found on the Park website:
http://www.parktool.com/repair_help/...ualpivot.shtml
Their complete listing of bike maintenance guides can be found at:
http://www.parktool.com/repair_help/FAQindex.shtml
or, you can take your bike to your local bike shop and they should be able to adjust it for a minimal charge.