The volume on mt gox is small compared to say nyse, you probalby don't even need to query every 2 minutes...

I wrote a small perl backend to show these charts. (I couldn't find a chart site that let me view by date).

http://bitcoin.coprimeinc.com/

I'm still experimenting with it. The perl backend took me about 10 minutes to write - which grabs the trade data off mt gox and dumps it into mysql.

PM me if you want more details.