In my opinion, the hardest references to find are ones concerning figure drawing for scenes and individual poses- odd angles, multiple subjects and especially those scenes where there is action going on, like a fight. What should you do? Where can you find copyright free references to use in your artworks? You can make your own - free. Here's how:
Daz3D Studio- I'm putting this one top of the list because I think most people will find it the most appealing, and with good reason. The basic program and models are free. There are hundreds, if not thousands, of models, props and outfits in their store for you to purchase and add to your models and scenes. The models are beautiful. When working with the models setting up a scene they feel very lifelike- as if they actually had bones and muscles inside their bodies. Pretty cool. I admit having a limited knowledge of this program because it is a little overwhelming to use with all of it's options. Basically I haven't taken the time out to actually learn how to use it, so it is me being lazy. Overall I am very impressed with what I have seen and I really need to make a point to get more familiar.
Poser - At the moment this one is my favorite. This is the Poser 6 version. I got it as a gift years ago and it has served me well. While this software isn't exactly free (various versions have various pricetags) it is easier to use than other programs. You can set up a scene and render it in minutes. Figures can be displayed as full or as boxes. I also like that the interface is drag and drop and the posing window can be resized. The only real downside is that the models are not as lifelike as the models in Daz3D Studio, at least in my version. The link I have provided will get you a free trial version of Poser 10.
Make Human - I have to admit that until I started researching for this article I had never heard of this program. I decided to go ahead and include it because it is a 100% free open source program. Should you be so inclined, you can code for it and make your own versions. I also am intrigued by other features, such as the sliders to change the race of your models. I'm curious to know if you can set up scenes with multiple models. I think it warrants further investigation.
Posemaniacs - This is not as customizable as Poser or Daz3D, however, there is an app that will allow you to use it on your smartphone. There is a huge library of poses that can be rotated 360 degrees. Sadly, this only applies to Y axis. It is free, although, you can make donations on the website. More poses are being developed.