Or you could not have everyone in your party blow a feat that they may or may not even be able to take. Not that it isn't fun to have a freakishly undead-like party, but it's really a hard sell in many cases. My suggestions are going to differ depending on just how min/max you are going here.
If you want to go as far as possible a well constructed artificer is your best bet. You would be able to laugh off wounds and effects that would kill a regular old cleric, but it takes a lot of book keeping and a lot of people hate artificers.
Cleric is really a very solid base for healing though. You can do really over the top DMM tricks if you want to be superman, or just stick to traditional healing and still be somewhat effective.
If you want to be a traditional healer there is actually a class from miniatures handbook called healer. They have an edge over cleric at traditional healing, but they are far, far worse at everything else. Maybe play a pacifist healer? Take vow of peace or some such thing.
If you want my personal favorite healing tricks I will list them below.
Sacred Healing (Feat, Complete Divine) grants area fast healing for turn attempts. A good solitary healing ability.
Dragonic Aura (Vigor) (Feat, Dragon Magic) gives you an area of fast healing up to half hp, but it's constantly on. Bonus if you can swing dragonblooded subtype.
Martial Stance (Martial Spirit) (Feat, Tome of Battle: The Book of Nine Swords) this one heals you or an ally within 30ft for 2hp everytime you make a melee attack. It lets you multitask.
Augment Healing (Feat, Complete Divine) adds potency to healing spells. It isn't that much, but it's nice to get for a dedicated healer.
Master of Day and Night (Feat, Player's Guide to Eberon) maximizes all cure spells.