I turned off the interior water main (gate valve, I think) to do a minor repair, now I can't get any water to the house. What can I do to fix it... really need a shower in the morning. Thanks!

If it is gate valve than chances are yoke got stuck in closed position. It is a common problem. You will probably have to replace the entire valve with new ball valve...

But for now - just to get your water running again - close water at the curb, release pressure, remove valve handle, unscrew the bonnet nut and remove the stem the valve handle is attached to it. Locate and remove yoke and toss it.

Screw back in the stem and tighten the bonnet nut. Now you have running water - but non-functional valve. Buy new valve and replace the old one when time permits.