I found that most of the worksheets and lessons out there weren't very useful to me, so I create a lot of stuff on my own. My activities are highly customizable to fit your needs. Much of the work I put into it is centered on searching through primary source documents and excerpting them down to sizes that are more manageable for students to tackle. Generally, the worksheets that come with my textbooks aren't challenging enough to hit the full gamut of student abilities, and I try to have a wide array of questions that can push students of all abilities.
If you've also been frustrated with the lack of quality and rigor, I hope you find something worthwhile in my store!
Profile photo cropped and shared under the Creative Commons 2.0 License
https://creativecommons.org/licenses/by-sa/2.0/legalcode . Original photo from Flickr: http://www.flickr.com/photos/limaoscarjuliet/225249268/