1st pic looks like a stomatella snail. Definitely keep these guys. They are good to have.
Im not a huge fan of bumble snails as they have been known to go after other snails if there is not enough food for them. Though they are usually peaceful, keep in mind that the Bumble Bee Snail is essentially a carnivore.
Here is a couple good links for you to ID some hitchhikers you may come across.
http://www.xtalworld.com/Aquarium/hitchfaq.htm
http://www.melevsreef.com/id/
http://www.chucksaddiction.com/hitchhikers.html