Sam Nelson left The Madlads in 2008 to pursue other projects. While his departure was never officially announced, it was confirmed in an interview with his former partner, Matt Besser, in 2014.
After leaving The Madlads, Sam Nelson moved away from the public eye and hasn't been actively involved in comedy or entertainment since. He's not on social media and there's little information available about what he's doing now.
However, it's worth noting that The Madlads, with Matt Besser continuing as the sole member, still produced content on their website and YouTube channel until around 2013.
Therefore, while there's no concrete information about what Sam Nelson is up to these days, it's clear he chose to step away from the spotlight after leaving The Madlads.