Linux as a router/gateway

[Jeremy Fowler]

How hard would it be to setup a Linux box to route Internet traffic to two
separate DSL routers? Here's the setup, small office with 2x 256Kb DSL
routers/connections. This office was too far away from the CO for anything
faster and the ISP's DSLAMs didn't support bonding of the two DSL lines. So, now
they have two connections to the Internet and they split the traffic in half by
assigning specific IP address ranges to the different routers with DHCP. This
isn't very efficient if one side were to utilize bandwidth more than the other
side. I had an idea of setting up a Linux box to route traffic to the two DSL
routers directly and then set this Linux box as the default gateway for the
network. This box would have three NICs one to each router and then a third to
the LAN. How would one go about setting this up so that the Linux box would
utilize both DSL connections evenly and efficiently? Is there a way to do this?
Any help is appreciated.

Thanks,
Jeremy Fowler