So there's a subreddit known as /r/futanari and as you can imagine, it's a pretty top place to pick up pictures of dickgirls doing what they do best. That said, I think when you're hoping to jerk off, visiting the Imgur archive page of the content is a hell of a lot more convenient than going to the subreddit and clicking on all of the material one page at a time. So, to make your life easier, I've gone ahead and linked directly to the Imgur archive page of all /r/futanari material.
By default, the thumbnail display is organized based on the newest updates, but you can choose to alter this and put it on a setting for the 'most viewed'. There aren't too many comments on the Imgur hosting segment, but with direct links to the Reddit threads, you'll have no issues finding sources and names so you can get your hands on more dirty dickgirl hentai.