Depends if you're after linework or filled, but the one I use most often is from BFC:
http://www.bfc-creations.com/Designs500/526Greyhounds/index.html
I also love a set from Huskey -those are part filled and are slightly caricature style and fun as well as quick to do.
Skeldale House has an embossed greyhound and I think I have a greyhound from Advanced Embroidery Designs as well. For a light and quick design for hankies etc I have one that I think is from a Chinese site where the design names all start with EWG, if that helps. You need to look through lots of pages there, though. Embroidery Library also has a filled one as well as a decor style swishy looking one. Last but definitely not least, our very helpful cutie, Vicki, AKA Basketcase, has done some whippets and a lurcher, which are close enough :)