Western Digital Scorpio Black wd5000bpkt 500GB 7200 RPM $70
Western Digital Scorpio Black WD5000BEKT 500GB 7200 RPM $75
wd5000bpkt is the best!!!
Based on benchmark: http://www.harddrivebenchmark.net/common_drives.html
Based on review: http://www.newegg.com/Product/Product.aspx?Item=N82E16822136856
BPKT is using 4k sector, but BEKT is using 512b sector. Therefore, BPKT doesn't have compatibility to old computers, but it's usually fast for read and write.
Western Digital Scorpio Black WD7500BPKT 750GB 7200 rpm $110 could be alternative.