Frys.com has 1gig of Kingston PC-4200 (533 MHz) DDR2 SO-DIMM ram for $75 + shipping, and no tax for most states, cheapest in-store is $130.
http://shop1.outpost.com/product/4465146?site=sr:SEARCH:MAIN_RSLT_PG
Model #: KVR533D2S4/1G
http://shop1.outpost.com/product/4465146?site=sr:SEARCH:MAIN_RSLT_PG
Model #: KVR533D2S4/1G