For all the best information on donating to SSW, click on the Donate tab on the top menu.
From there you can donate to SSW through PayPal. Once your transaction is approved, you will be rewarded with E-Peen. You will be notified of your E-Peen's arrival through Smail.
If you don't have a PayPal account - or just have lots of extra singles laying around after your last trip to the strip club - you can always mail in a donation. The address and all the other important details are on the Donate page.