GenXer - have you been putting any money aside for taxes for 2004? If not, it's a good idea to put away a % of the money you get in that is not taxed (like checks from sponsors) so that when tax time rolls around, you have money to pay what you owe. I did this before I became an S-Corp & usually, I had more money than I owed to them, so that was a refund of sorts
As far as quarterly taxes, I think you have to pay in at least 90% of the taxes that you paid the previous year, so if you pay $1000 in taxes for 2004, they will want to see at least $900 from you for 2005 (or $225 each quarter)
Of course, I am not an accountant & you really should talk to one instead of taking my advice