I know tons of happy adoption stories or auction 'saves' buying horses off feedlots. In this day and age a lot of people are dumping horses because they can't afford to feed them.
There's a great group on facebook (probably quite a few) that have a great website filled with success stories of adopting feedlot horses. I often contribute to the 'bail' of such horses sending 10-50 bucks when someone offers a home but needs help raising the auction price.
Here's one of their websites. Click on the available horses (That have been evaluated as good adoption candidates) and their success stories. Also look at their bulletin board for the HUNDREDS of saved horses. Rebels Equine Sales
Their facebook page also has a lot of 'checkins' on horses a year + after adoption, pictures of first horseshoes, trail rides, etc. Its all very heartwarming. The great thing about the lot these guys save off of in Wa state is that the lot owner lets prepurchase vet checks happen too.
Here's some facebook additional info for your surfing pleasure:
Rebel's Facebook: https://www.facebook.com/groups/142328211252/
Another Sunrise Fundraising Site: Another Sunrise Equine Fundraising Network | Facebook
These people will help you fundraise (Sharing on facebook, calling friends, etc and give you the info to set up stuff like paypal accounts or help you get funding just by word of mouth) to raise a horse's bail price or auction fee. This one helps all sorts, but many auction sites have facebook supporters just for this info.
I watched six fabulous geldings, including two white arabs who were endurance horses get sold off the lot this week for 600-700 apiece and were absolutely fabulous horses with years left in them.
Currently they are fundraising hot and heavy for Azuza who's almost got her $800 bail raised. She needs to finish fundraising tonight because the kill truck comes tomorrow and if they don't have the rest of the money the Feedlot owner puts them on the truck.
Its a really good thing to do, to adopt a horse out of the horrors of slaughter. If you have the means and can get a good evaluation on a horse you want to adopt so you know what your getting into, please don't hesitate. None of our hoofed friends deserve an end like these slaughterbound horses get.