I often donate my BC books to charity-sale shelves, but I do mix it up with releases on park benches and other out-in-public spots. (As per my post in that thread, thrift shops and charity shops vary as to whether they accept books with BC labels, and as to how long they keep books in stock before discarding or recycling the ones that don't sell. Different regions and countries may have different rules (official or otherwise) as well.)
The rest of that thread may also be of interest, and I recommend that you browse this forum and the Release Techniques forum for more ideas about where to leave books - and where not to leave them!
Also, check out the Site Watch forum - it can be reassuring to see books that have been caught and journaled, and may give you release ideas too.
It varies so much. Some charity shops won't take books with BC labels. We've heard that some rip them out. Or toss the books in the trash.
But some are fine with labeled books. I've found BC books at Goodwill and Salavation Army and the local used bookstore. (Whether they were okay with labeled books, or didn't notice the labels, I don't know.)
I don't think my charity shop would throw them out. But I can make that sure. I was also asking because of the fact, that they sell the books in the end. But it's not more than 50 Cents or 1€ per book...
The first time I ask them if they'll take them because of the label & I show them it. Local charity shops are always happy to accept them, but national ones, for example, Oxfam, British Heart Foundation, I've found won't. Also, I just make sure that any stickers that might be on the cover don't say "free book".
I've had the odd catch...good luck with your releasing :o)