Running lights work on my 2004 Ford F 150 truck, but the brake lights will not come on. Its not the fuses inside the cab.....any suggestions on what to check next?

There is a switch on the brake pedal that could have failed. Check there for power in. There may be a second switch if you have cruise control.

Thank you Tenspeed....if there is no power going into the switch...what next?

You have checked the fuse I take it, so if there is no juice to the switch and the fuse is apparently OK, you might want to change the fuse anyway, sometimes the fuse will fail but not show no obvious signs of doing so. Then check in the fuse box with a tester, either a 12volt light tester or volt meter, to see if there is power on the hot side of the fuse connection, just jump the empty fuse socket with the tester

And do the turn signals work OK?

I found an answer - there's a $13 brake sensor above the pedal - read about it here - > http://www.f150online.com/forums/electrical-systems/147800-brake-light-failure- fuse-good-thoughts.html