With the correct IOS, a substantial amount of RAM (preferably 256 megs of RAM) and the appropriate WIC card, you can run full BGP tables on the router, which would allow you to manage 2 internet connections. You'd need your own BGP AS, public IP addresses, and a maxed out 1760 router. Even then, though it could do it, it would possibly overload when loading the full internet tables. If you want to run 2 internet connections, I would more likely recommmend the 2800 series router.
You don't need BGP if you only need to have outbound load-balancing. Take a look at this:
Also, Cisco has a similar article:
In either case, load-balancing inbound traffic will be a challenge, even with BGP. I've done this where one link is used for traffic initiated from internally, the other externally. This simplifies NAT and still allows for one link to fail, provided you're using some sort of DNS failover for your external services.