Zetsu's Spore Technique creates clones, which feed on chakra to grow are also able to transfer chakra to people they come in contact with. Dan Katō was able to use this technique as a spirit in Tsunade's consciousness to restore her chakra and Yin Seal.
The Magaki Group uses this technique in a different way. First Nangō sends his chakra to Benten and Chūshin, and then both of them send it along with its own to Akaboshi, greatly enhancing the power of his techniques.
The Tailed Beasts are also able to freely share their chakra with whomever they choose, and as Kurama has noted, it is a less complicated process for them than it is for humans.
Certain people, such as Minato Namikaze and Naruto Uzumaki could also mould the transferred chakra in order to adapt it to another person's specific chakra type. In the latter's case, due to Kurama's chakra, it also enveloped the recipients in a chakra cloak similar to his "Version 1" form, albeit with no tails.