I worded it wrong, sorry.
Passive as in a support who isn't poking every few seconds, and primarily focus on making sure their carries are safe and strong.

Soraka is passive. When Soraka is in the lane, the ADC is not.

Yes, I call sitting there sustaining ****ing passive. Plus the damage Infuse does is less than the ADC's poke, so it doesn't truly count as useful harassment.

-Scorch

Soraka, Janna. Soraka for the HP/MP sustain, Janna for extra CC in the lane, plus she has the shield. Taric also deserves honorable mention.

-Banister

Good skins are always a plus. I have a skin for every champion I main ^^
^Reason for moving towards Sona. I really don't mind pokey supports as well, I often have a blast with every game I play Lulu with.

Easy to say on this Thread. Although support should be harassing more, they could just stay back, and let the AD Carry harass as well.

Soraka - Passive support. Silence your enemy when they get close, n give free mana
Janna - Spam that Shield. Gives free AD damage and a protection.
Sona - Sona isn't really a passive support. If you want to be good, you have to use the powercord (passive) on the AD. Q + Powercord hurts a lot. Along with that ult.
Nami - Just make sure you land that heal on your enemy, so it can bounce.
Taric - Really aggressive. Better land that stun n heal your ally..
Leona - Same with Taric.
Lulu - One of my favorite. Just land that Q to slow n harass a lot

You seriously underestimate the power of that Armor buff and what a few points in E will do to a squishy carry or support. (If you're playing her against some tanky support, you're more than likely countered anyway. That's about the only time I'd see playing passive to be a better option.)

Janna is more about shielding and peeling for her carry. You should still be aiming to throw out some autos where it's safe to, but generally you won't be casting much other than shield unless you're trying to keep something off your carry.