Now while I'm more than happy for this to be the case, I was a little confused when I checked out Gay Video Shack on Tumblr and saw that the latest two posts were a still image and a 2-second GIF. Thankfully, scrolling down a little showed me that around 80% of the posts on this blog are devoted to what the doctor ordered: gay guys having sex in front of a lens.
The blog seems to focus a little more on professional adult entertainment as opposed to your standard production that features on Tumblr: that of amateurs. The content doesn't update here as often as other sites, but it's still a whole load better than nothing.
Probably not the type of Tumblr blog I'd visit in and of itself, but you can bet your ass it's worth a follow if you want clips of gay bros going at one another.