Hello Sam,
as Brent suggests you should look at eBGP.
the limit of IGP protocols like OSPF or EIGRP is that the two providers cannot accept to exchange routes via your router.
using different OSPF processes or different EIGRP processes doesn't produce a load balancing effect:
EIGRP with lower AS number wins
for OSPF the first process to propose a prefix to IP routing table mantainer wins (ships in the night)
also OSPF route types are not considered.
for BGP multihoming example see
http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a008009456d.shtml
Hope to help
Giuseppe
