The Hitachi Travelstar 7K320 (7200rpm, 320G) offers the most bang for the buck in terms of capacity to speed ratio to price ratio. It tops out at 75MB/s READ and WRITE. It's going for $79 after double rebate on ZipZoomFly.com.
But for blazing speed at an 'almost reasonable' price with 'adequate' storage capacity, the OCZ Core Series 128G SSD is tempting. We measured 103MB/s READ and 86MB/s WRITE. You can buy it at Amazon for $349 after rebate.