From Tom Shinder:
For years we’ve been asking for multiple ISP support for our ISA firewalls. Well, that never happened, but the great news is that TMG firewall now feature multiple ISP support. You can use two Internet connections, either for failover or load balancing. You can even set different weights on your ISPs, so that more traffic go through the faster link.
Forefront Threat Management Gateway (TMG) is the next generation of the ISA Server product line that has been rebranded and enhanced with Forefront anti-malware functionality. You can download Beta 2 of Forefront TMG from Microsoft here.