Good places to donate books are: your local library (make sure they can use them), shelters, schools, daycare programs, literacy programs, hospitals, hostels, and of course used book stores.
Ways to accumulate fewer books: use the library (including inter-library loan if your local library doesn’t have what you want), trade books with friends, create a special interest library for club members, institute a "one in, one out" rule.
Resource ListGet Organized and Stay Organized
New Years Resolutions
Decluttering and Organizing blog
Robin’s organizing and decluttering safari
How to Declutter Your Unfinished Projects
How to Start Dcluttering Your Home
Decluttering Before Organizing
Zen Habits – How to Declutter