It looks like Mushkin has come up with some great ddr2 memory. Check out a review of the Mushkin 1GB PC2-5300 (667) DDR2 Dual Pack at OCTools.
“We were able to take Mushkin’s PC2-5300 up to 706MHz DDR2 at CAS 4-4-4-11 and up to 760MHz DDR2 at CAS 5-5-5-12 with the memory voltage set at 2.0v”.