You could get the free Asterisk IP PBX with two FXO ports to connect to two phone lines coming into your home. Configure it so that you can dial in on one line and then dial out long distance on the other using an access code.
I'm not even sure that's possible but it sounds like a good idea. :) I'm sure someone with more experience than I have (that wouldn't be too difficult) will have a few better ideas.
The is another nice benefit to my idea if you have this IP PBX connected to the Internet. If you are at another site that has high-speed Internet access you could dial into your home PBX using a softphone via IP instead of using a landline. That would be especially useful if you were out of town and needed to make a long distance call. Regards, John