There is also a sub-forum specifically for digital stamping here. There is a thread that lists a lot of digital stamp companies. Not all of them are active anymore, but the major ones are listed in there. Here's a link to the thread: Digital Stamp Companies
You can also find a lot of nice digital stamps from the free digi stamp blog: Free Digital Stamps
Good luck finding what you want. I know I could spend hours going through and picking up all the cute freebies along the way.