I have the same problem! It’s never-ending. My collection is vast, and most of it is no-longer-current, but pristine hardcover and trade paper non-fiction, with occasional literary fiction in various conditions. For what it’s worth, this is what I do:
1. List certain items on Amazon marketplace. Only if my copy is pristine, and the competing sellers (in the New category) are charging over $20 – not worthwhile otherwise. I will sometimes price my copy higher than the best price for comparable copies, because pricing it lower simply triggers competitors to lower their prices. No point. Give brief, but explicit details about condition. People like that, and will pay a little more to know what they’re getting.
2. Anything scholarly (your philosophy books), esoteric, etc. (no mass-market stuff) should be boxed up and brought to a good used bookstore. Try phoning first – are they looking at new books? No point carting them around if they’re going to say no (they are definitely not all drooling for new stock. Many are overflowing as it is).
Be prepared to describe some of what you have. You may want to visit more than one shop in one day, but some will expect you to leave the box(es) and come back another day, if they remember to call you. You can ask them if they’d like to give you a price on the whole box. That way you don’t have to bring any home. But do this in person, and not on the phone.
The whole process requires some patience and some preparation for heartbreak – they may not want much of what you have to offer. And if, as you say, it’s physically difficult for you, you should bring someone to do the carrying – just be sure to tell them not to talk during your transaction (trust me). But you certainly don’t need to make lists of titles. They’ll need to physically handle the books anyway, and likely won’t want your list.
3. Garage/lawn sale. I haven’t done this yet, but will probably resort to it this summer. If you don’t want to tend it, perhaps bribe hire a young person or family member to do it? Put out boxes marked $1, $2, etc.
4. This works best in a big city like mine: put books out on the curb in a small pile marked “FREE!” They will typically disappear within an hour.
So, yes – an Amazon marketplace is tedious to set up, but the thing I like about it is that I can list a book and ignore it for literally years and then have it sell for $50 even if it isn’t worth a tenth of that. The other options are all annoying in their own ways, though you’ll know almost right away whether you can get money for them or not.
I have only just started trying eBay, and have not seen any action there yet. Their listing process is many times worse than that at Amazon marketplace, but you can bundle your books (as you asked), whereas you cannot do that at Amazon.
I will also add that although @Seek recommends libraries, there is not a single library here that would welcome used books. I’m sure this must vary regionally, so see what it’s like in your area. For pure donations, I agree with the nursing home suggestion, and you might also try homeless shelters, or churches (though that would not be my first choice).