Posemaniacs and Timed Gesture Drawings
Posemaniacs is a great little browser app that lets you set up short life drawing gesture sessions at different timed intervals (30 second gestures being the default). The app draws from several thousand poses of anatomical 3D modes, and you can also set it to rotate them randomly (advanced mode), work in silhouette only (the Negative Space link on the side), and a few other options.
In addition to the timed app, there’s also a full library of all the poses that could show up in the app further down the same page, which can be rotated and viewed for however long you like if you feel like a longer drawing.
Finally, there’s a much smaller- although still awfully useful (I was going to type handy there until I caught myself and realized how stupid that would sound) library of hands, feet, and busts if that’s an area you want practice in. The first image that will show up there is a nude male bust, just as fair warning to anyone planning on opening that at work.