I trawled through the 500 most recent entries and picked out 10 free devices with a variety of functions that are actually pretty cool (and seem to be stable, I didn’t put anything on this list that caused any crashes). So, to get to the point, I’ve gone and done you a solid. Third problem, a lot of the most popular stuff is now very old, and superseded by official Ableton Max For Live packs, so that also makes sorting by ‘most popular’ a little annoying. Second problem, supposing you’re not in a spending mood, there’s no way (that I’ve found anyway) to sort by free downloads, which is pretty frustrating. To put it less kindly, a lot of them just don’t bloody work properly. So the devices that are available for free, vary in their stability and usefulness. Being an open platform, any level of programmer can upload their devices - from complete amateur to professional.
Since 2009, savvy programmers have been sharing custom built Ableton Live devices via the website, resulting in a library of almost 4000 devices available to download and use in your own projects. Musician’s are not limited by the effects, sequencers, instruments and mixing utilities included with Ableton - if you can think up a device, odds are it can be custom built within the Max For Live programming interface.
With its Max programming language integration, Ableton Live is a tinkerer’s dream.