While I do ride in the rain, I also take the opportunity to clean the rafters in the barn of cobwebs, carefully go over the barn/stalls/corrals/fences and make repairs to them. Tack gets cleaned extra well. Stall floors get leveled and repacked.
Otherwise, I make rope halters. My boss makes bridles, reins, breast collars and standing martingales. I condition them. We keep a bunch on hand at the trailer for anyone who has an equipment malfunction.
Or, pick up a book at the library on braiding. You can start by practicing with baling twine. A friend makes door mats from baling twine, too. They are sturdy and great for cleaning mud off boots at the door. They are ugly, though!