I found 2 free DLC available for Payday 2 from -
http://www.epicbundle.com/game-deal-voucher but like others have mentioned above, the site was overwhelmed. I finally got in and it is just an HTTP redirect to a "Ultimate edition is coming soon, please buy it for $45 USD" bait-and-switch page.
Grateful for the free game I got the other day, but the dev/pub are pretty terrible with DLC and consumer friendliness IMHO, and the bait-n-switch is just another example of it. It is nice to see they're making an all-in-one ulitmate edition of the game and suggest that they're going to make all future DLC free, but they kind of boned their original customers a bit in the process because nobody can buy the DLC now anymore and are forced to re-buy the game at full price. It might be cheaper than buying all the DLC at once as they say, but then some people don't want all of the DLC. If they wanted to truly be gamer friendly they would provide both options IMHO.
Having said that, the Payday games are pretty wicked from what I've seen. Hopefully this free DLC thing gets sorted out today/soon though and I can give them a pass on the baiting.