A lot of it; regular household, latex paint.
I used a big spoon to scrape off as much as I could, but couldn't get it all up. Now I'm not sure what to do, how to get the rest off, if I even can. Fortunately I spilled it on the closet floor, not in the middle of the living room.
If you have a steam cleaner - using that with detergent or brand laundry detergent might help get a lot of it. Or possibly hot water with detergent of some kind. Then go at it with something that removes solvents (so rubbing alcohol or commercial glass cleaner would work out). At worst - I think I've heard that something by goo gone (maybe goo gone 2) works well for latex paint too.
Vodka or nail polish remover (with acetone, not without).
Dab dab dab dab dab. DO NOT RUB. It will come out. I used nail polish remover on green latex in the middle of my almost white living room carpet. That had sat under a drop cloth for about 4 weeks. It got it all out.
I spilled about 1/4 of a can on my carpet once and was able to get it all up. It took awhile, but it worked!
I read to use water and scrape it up on the internet.
I just poured water over it, scraped it with spatula type utensils into a pitcher. I did this over and over until most of it was up. Then I poured more water over it and soaked the remainder up with a towel.