Is There A LinuxOS That Can Handle Load Balancing/WAN Redundancy?

[bluegrass]

I have two (2) DSL Lines from 2 different providers (2 different routers and gateways), I was wondering whether there is a LinuxOS which can handle Network Redundancy or shall I say, I'll just plug-in three (3) network cards on my Linux Box, 1 for my private network and the two other cards will be used for the two DSL Lines. Then I'll just program "load balancing" on the Linux Box.

Isn't it that this would be much cheaper than buying a hardware to do WAN Redundancy?