There are a lot of ways to support Slackware Linux Project. One of them is by subscribing to Slackware Linux CD/DVD releases or by using Slackware Store to purchase merchandises or even donate to the project.
Ruario was asking on LQ about Patrick Volkerding's CafePress account and it seems to be legitimate as Pat answered himself. This is a good news for those who would like to buy Slackware merchandise, as this site offers items that are not available on the Slackware Store. Since this account belongs to Patrick, you will also support him directly by purchasing items from this site, so basically you have two options: Slackware Store or CafePress.
All of the items sold here are using the flippy logo which was introduced in Slackware 13.37. It's good that that logo remains favorite to some people, including me.
I have just bought two items from this site: Hooded Sweatshirt and Long Sleeve Dark T-Shirt. Let's wait for few weeks before they arrived at my house.
Happy Purchasing :)