My plan for Venus

Culture a ton of that, load it onto a rocket with a dispersal system and disperse it into the atmosphere.
 
Better yet, set up a moon base for manufacturing rockets and helium 3 (in the soil, great rocket fuel) and send one ever 1-2 months for a decade or two, then go out to the asteroid belt and mine a ton more raw materials and get an automated production facility pumping out rockets full of that extremophile and just keep hurling them at venus... it'll eat up all the co2, and generate absurd amounts of bio-fuel... just collecting on the surface until the co2 is considerably reduced and you can just land.
 
Better yet, find/engineer one that eats up the carbon and just releases oxygen.... It'd be a super oxygen rich environment after a while (you'd have to do it way past the 20% that Earth has because you'd need to reduce the pressure and subsequent temperature the CO2 is making but meh)... Venus is 96.5% co2 and only 3.5% where Earth is 78% nitrogen 20.95% oxygen and CO2 is only .03% so you probably could go colonize it BUT if you could reduce the pressure and heat I'm sure there are depoits of all the ores you'd find on earth you'd need for construction. Also deuterium and hydrogen in the atmosphere in greater quantities than here.
 
Generate the oxygen, combine with hydrogen... water. Set up work colonies, mine, refine, fabricate metals and parts you could launch into orbit using oxygen rockets or even biofuel. Lots of sulfuric acid so you can make fertilizers for the work colonies also use it in production of explosives for the mining operations.
 
It'd give us excellent skill with working on a foreign planet, not to mention give us materials (while of course we are mining the asteroid belt too, more material out there than 100, hell 1000 earth's)... then I'm sure you find something in the soil you could convert to nitrogen and turn it into Earth 2 (if in fact Earth isn't Venus 2)... Mars will never be an option as the atmosphere is just gone.
 
As we continue to mine stuff in the asteroid field and work towards FTL propulsion or at least near speed of light (which we can already due with nukes, look at Project Orion)... we'd have materials to build massive ships, probes, sattelites etc to start spreading around our solar system and sending out of it. Not to mention we could jsut produce giant ships in orbit near Earth and the Moon, near Venus and Mars that could be life boats, as well as look like a giant navy in the event hostile ET's show up and see these massive ships parked around the planets that might make them think twice about attacking us (we could also load them with massive projectiles made from mined asteroids as massive impact weapons to use against invading enemies like in the Lost Fleet Series)...