Bridge it with a piece of thin wire and connect the battery (properly) but don't turn anything on. If the wire blows instantly you probably have blown the diodes in the alternator. If the wire holds, it is safe to install a new fuse. Again do not try to run the car this way, wait until you have a proper fuse.

 

sorry, it was an 80 amp fuse (Typing too fast LOL) but my alternator was seized anyway, so i have that replaced now. The fuse is the only thing stopping me right now from my engine running. I put in a new battery last year and it still holding a 12.55V charge so there was very little drain over time.