I had a 97 Tacoma with drum brakes on the rear that needed frequent servicing. I live on a dirt road and did a lot of off roading...so if this is the first trouble you've been having, you're lucky. Get it serviced asap. With the light back end and slippery conditions later in the winter, you're asking for control problems. As the brake shoes wear, they can get hung up and bind, then release with a thud. If they remain dragging you can really heat up the the area putting other components (bearings etc) in jepardy.
They need to be lubed and serviced regularly after you have a rear brake job (new brake shoes probably), as the protection for parking brake cable and other components, really isn't that good. The parking brake engages the shoes as well and often cause the the drag and premature wear, resulting in the problems you described.
I crawled under regularly when I changed oil and "painted" the areas with problems (parking brake levers and cables and yoke esp.) with red grease. Removing the yoke and greasing is a good idea as well. They should do all this when you have it serviced. It will cost a bit of $$$$ like all brake jobs do.