I am a big fan of reusing ziploc bags. I reuse all of my ziplocs that have not had raw meat in them. I use them until they simply give out and get a hole or spring a leak.
If they have held something dry (crackers, cookies, etc.) I usually just empty the crumbs into the trash and stick the bag back in my stash. However, if they've held another type of food or something messy, I wash them by hand.
My tip for you is to hang on to your bottle/sippy cup drying rack once you're no longer using it for its intended purpose, it makes a really good baggie drying rack. I also frequently have more bags to dry than will fit on the rack so I move my utensil bucket onto a towel and place bags onto taller spoons and spatulas to dry. Here's what my kitchen counter looks like on those occasions.
Be sure to head on over to Kitchen Tip Tuesday for more wonderful tips to make your kitchen time go more smoothly.