Bullseye handmade glass from Portland,Oregon USA is the A-brand for fusing for many years. Glass fusing is the melting of different and/or the same colors of glass to create glass objects.
Also take a look at http://www.bullseyeglass.com or download the Bullseye catalogue. 
Qualities of Bullseye glass
1. Still good compatibility after three firings.
2. Compared to other brands of compatible glass, Bullseye hardly suffers from divid 
3. Compatibility. Bullseye has control over both the expansion coefficient and the viscosity of the glass like no other.

Frank van den Ham