You might want to look into running an S Corp or LLC - you pay yourself a salary - which is taxed just like before, but you pay the rest in distribution where you don't have employment taxes.
Talk to a decent accountant or read some books on it. It really isn't that complicated once you learn about it, but before you do it can seem overwhelming.
Taxes are almost every successful persons biggest expense - so you need to treat it as such and reduce it as much as you can.
I have read thousands and thousands of pages on tax stuff. Don't get sucked into any of the scams. You can take advatage of deductions, S Corp status, and retirement plans, but other than that - there aren't many good legal loopholes.
Keep in mind even if you don't go with the S Corp - you still don't have to pay the full 15.3% if you make over 87,000 - you pay 2.9% of the amount over that. And this is combined with your regular job if you have one.
So if you make $50K a year and pull $37K in in internet income - anything above that is 2.9 and not 15.3.
I'd hihly recommend anyoneinterested in learning more about taxes buying the following:
J.K. Lasser's Your Income Tax 2004
It doesn't really go into the different forms of businesses that much, but you will know almost everything you need to about income taxes.