I do enjoy all the sites mentioned but wanted to add that Oregon PatchWorks does have really lovely freebies each month and some very good sales weekly/monthly from a large variety of different designers (well over 100 digitizers) - something for everyone's tastes. (I'm not affiliated with Oregon Patchworks, only a very satisfied member of their Yahoo Groups). Their weekly newsletter has good tips, shows new designs, posts free designs and has a variety of contests. Their site gives you a good idea of the types of designs that can be done on an embroidery machine allowing a person to choose their favorites. No membership is required to purchase; only a free membership for the weekly freebies.
Their address is as follows:
http://www.oregonpatchworks.com/site-map.php