luhman.org

Yahoo is a pretty good source for historical stock and ETF prices. For example, here's a link that will provide historical prices for the SPY ETF :

http://finance.yahoo.com/q/hp?a=10&b=19&c=2008&d=08&e=10&f=2011&g=d&s=spy

The link at the bottom allows one-page downloads of CSV content, or you can try this link :

http://ichart.finance.yahoo.com/table.csv?s=SPY&a=10&b=19&c=2008&d=08&e=...