Speedy Janna Build
This build for Janna Support focuses on high movement speed to get you where you need to be in order to make the most of your abilities. After some hard testing, at full build, Janna has 551 MS normally, 986 coming off the font with homeguard, 490 while Zypher is down, 638 with Talisman active, and 1073MS if coming off the font with Talisman active. That's with these items and masteries.
The items built: Talisman Of Ascension, Twin Shadows, Ardent Censor, Boots of Swiftness(With homeguard), sightstone, and finally Luden's Echo.
Masteries: 9/0/21 and has 10% CDR built in. http://goo.gl/WHztWZ Runes: 9 magic pen marks, 9 mana regen seals, 9 max mana glyphs, and 3 AP quints.
The cost to full build is about 12k gold Luden's being the last item built. At full build it grants 220 AP 30%CDR(you get 10 more from masteries), And you get the following traits from the items. a) The speed boost from Talisman. b)Twin shadows seeking slow. c)enhanced shield from Ardent Censer boosting AAs even more. d)End game damage burst from Luden's
Cons to this build: You are squishy and must rely on your speed to avoid skill shots. Your damage is minimal till you get Luden's.
I have 2 videos up for this build in action: https://www.youtube.com/watch?v=wEQM-9C_UC0 and the follow up vid: https://www.youtube.com/watch?v=3A2mF-ZHtl4
Sadly I don't get to full build in either of these and will post another vid should I do so. Hope you enjoy.
you're already getting +200% mana regen and with the support masteries you already get 75 extra max mana. And janna is so squishy that the armor seals/mr glyphs are a necessity. Actually I'd also switch out the magic pen marks for armor marks because janna doesn't do a lot of damage. Also while maxing your movespeed is fun, it's not all that useful for winning the game.

and you're set. You can even switch out mobi boots for ninja tabis to add survivability.