It's unclear exactly when the updates began rolling out, but based on the fact that Friday people were still speculating as to when the update would come, it had to begin being pushed out sometime late Friday / early Saturday.
The update (VS740ZVD, Android 2.2.1) brings a ton of improvements to Android, including performance improvements, the ability to move apps to the SD card, improved security, and more.
Verizon LG Ally owners can now wave their devices in front of their Verizon Samsung Fascinate brethren. The only Galaxy S smartphone, of which the Fascinate is one, to receive a Froyo update is the T-Mobile Vibrant, and that requires a cabled install using Samsung's Kies desktop software.