There are lots of places to donate things, and Goodwill is not necessarily the best. Not because they're not an excellent organization, but because they're the most well-know and they're frequently inundated with mountains of stuff that they can't possibly sell. The market for used goods is not large enough to actually use all the donated items. A lot of the clothes that the Goodwill receives are shipped overseas to be recycled as stuffing for (guess what?) stuffed animals!
Children's books and stuffed animals are frequently welcomed by homeless shelters, women's domestic violence shelters, the Salvation Army, and probably many other places that serve people in crisis in your community (depending on the size/demographics of your city or town).
If you make a few phone calls, you can probably find out who needs what in your city and then sort your "give-aways" according to that. When we were de-cluttering, I would keep a box for the Storehouse, which serves homeless and near-homeless families (clothes, household items, children's books), a box for a domestic violence shelter (baby equipment, formula samples and coupons, toys and stuffed animals, my clothes from when I worked that would be suitable for a job interview), and a box for a men's drug rehab program (dh's "outgrown" (oh my gosh, he'd kill me!) work clothes, again stuff that was suitable for a job interview). If I had anything big like appliances, we called a local charity that will pick-up that stuff for you. AND, they don't care if it works or doesn't because even if appliances can't be fixed, they can often be a source of spare parts.
So, we'd load the boxes into the car and make a loop through town, dropping our boxes off. The people who took our donations from us were often thrilled that we'd put some thought into what exactly was needed. And, now that we don't buy "clutter" anymore, we sometimes have money to donate to these places. I'll tell ya', there's nothing like taking a case of tampons to a women's shelter to brighten everybody's day. :LOL We actually did this, and the young girl at the desk called the director out to see what we brought, and the director cracked up, and then told us it was absolutely perfect. People bring diapers all the time, but what about Mom?
OK, maybe too much information, but this worked great for us, and we felt good about it. I would have been very upset to see that usable stuff go unused and worse, to the landfill. Besides, our family has a reward system based on how few bags of trash we can generate in a week, and we didn't want to miss out on our weekend movies or bowling! We also learned our lesson and now buy 90% of our clothing used. People are out there getting rid of really good stuff!