Is there a quicker way to clear large amounts of lava other than...

[daimoth]

... actuating blocks over a large amount of it and reloading the world?

 

[Snickerbobble]

Yes, drop a lot of sand or other falling block in it then reload.

 

[daimoth]

Yes but then you have to recollect the sand. With actuators you just deactuate the blocks, let more lava flow in, and repeat.

 

[Baconfry]

This is a bit of a hassle, though. You should check out these two suggestions that aim to do something about it.
http://forums.terraria.org/index.php?threads/watering-can-a-new-gardening-and-building-tool.5184/
http://forums.terraria.org/index.php?threads/magic-sponge.5165/

Having it spread out over a long flat area can clean out small amounts of the stuff, but other than that, it looks like reloading is the only way to go.

 

[daimoth]

Decent ideas. A suggestion I made on the subreddit recently was to make the Heat Ray destroy water blocks.

 

[Matsu]

Well, depending on how close you are to the Underworld you could just dig a tunnel and route it there. If you're looking for removal the good old bucket method is surprisingly quick.

 

[daimoth]

I'm actually clearing the underworld itself of lava, more as an exploration of mechanics than something I need to do. Long story short, It's the world in which I learned to make liquid generators, and sections of my underworld are completely submerged in lava. Three guesses as to how it got there.

Anyway, actuating a staggering amount of sand over large swaths of lava is - as far as I can tell - the best way to deal with a truly intimidating amount of lava.

If you're talking about your garden-variety natural lava lakes, the most efficient way to deal with those is to punch a hole through the bottom of the lake and drain it into either another lava lake or the underworld. Although over time that will result in underworld flooding as well.