CardPen is yet another card making program, available online at http://cardpen.mcdemarco.net. You can also download the project from BitBucket and run it locally.
CardPen can generate simple HTML pages of cards for printing up yourself, or convert your cards, screens, boxes, scorepads, etc. from HTML to PNG images at 300 DPI (or more) for uploading to The Game Crafter (or elsewhere).
CardPen includes presets for most common and many uncommon card sizes, as well as custom sizes, circular cards, bleed support, zipping of your generated images, TGC overlays, and turning your BoardGameGeek game collection into cards.
If you're familiar with the many other card making programs out there, then you might think of CardPen as HCCD online and on steroids. If you're not, then see the CardPen documentation for a list of them. (Suggestions for additions to the list are welcome.)
There is a CardPen Users Guild at BoardGameGeek for questions, template help, and trying to gather useful information in one place, or you can ask here.