Rather hesitantly I will say take a look at Sewforum.com. They have thousands of designs that have been contributed by digitizers. The reason I provide some warning is that some of the digitizers are really good and some are really, really bad! If you know how to "preview" a design and understand the basics of a good design, you can find some nice things for free, but buyer beware!
Personally I prefer to buy from reputable individual digitizers. Many designs are only $2-5 and they will sew well. If you post on the ISO area of sewforum, you can get some good recommendations.
Pam