While cleaning out my inbox I found an email from when I first started and I had forgotten about. It has some pretty good site links on it. I'm including part of it so you can see what the user said about the different sites. I just checked and all of the sites are still working and some have some nice things. You can get anything from thread to stablizers from the.
http://www.marathonthread.com/
http://www.abc-machine-embroidery-designs.com/
http://www.longcreekmills.com/
I also have ordered stablilizer from the first 2 sites usually on sale on the 2nd site (abc)
These are a couple more sites I have ordered designs and software (I use Embird and love it)
http://www.stitchdelight.net/
http://www.secretsof.com/