I always have a hard time finding these… here are the current Paypal merchant fees (as of May 20th 2008)
US Transactions Costs

Monthly Sales
Price Per Transaction

$0.00 USD - $3,000.00 USD
2.9% + $0.30 USD

$3,000.01 USD - $10,000.00 USD
2.5% + $0.30 USD

$10,000.01 USD - $100,000.00 USD
2.2% + $0.30 USD

> $100,000.00 USD
1.9% + $0.30 USD

and seeing as I do [...]