I had a bit of a tough time deciding what sites I could show that are popular yet, not everyone had seen, or unpopular but I frequented. Besides, who wants to hear that I think the site Treehouses.com is amazing? Not that there is a lot to do there, I just think it's awesome that it exists.
So, instead of one really far out there I have a compromise, first for my "tail end" site I suggest Bird and Moon. The original comic "Bird and Moon" is several years old and the basis for Rosemary Mosco's popularity. I admit this probably isn't too far out there on the tail but I think it's under-acknowledged.
For my second site, I want to suggest popular site, only it helps you find those little tail-end gems. Toothpaste for Dinner (according to it's FAQ) generates 40 million hits a month, qualifying it as a behemoth of internet culture. The simple comics are fun and often clever. However, I want to draw attention to a subset of this site but before I do I feel the need to warn you that sometimes the images on this site are graphic. Click at your own risk. The toothpaste for dinner Livejournal Picture Generator Brings up random pictures recently posted on people's livejournals. some of the pictures are amazing and I've found many hidden gems of comics, blogs, and photos this way. Just yesterday when thinking about this assignment I found some interesting art. Or check out this, this, or this. This takes people watching to a whole new level.