Western Digital VelociRaptor 150GB 10000RPM SATA Internal Hard Drive for $119.99 shipped.  Here is a screenshot for your reference.  Note that it comes in OEM packaging, which means no pretty retail box but is otherwise identical.  For the technically inclined, it has a rotational speed of 10000 RPM and very fast seek time of 4.2ms vs about 9ms+ for most SATA hard drives.  Most places have it for about $139.