I know many of us no longer use textbooks and finding or creating resources is a pain.
I just came across the website www.math-aid.com and it is great for Algebra 1 and below.
This site generates a new worksheet every time, which is perfect for SBG. I wish you could combine different topics to customize a sheet. Unless I didn't figure that part out yet.
I also use the free stuff from KUTA, but I would like to check out the paid version one day. Kuta makes a good looking worksheet and provides enough room for students to do their work. Because I only use the free version, I am unable to generate different problems each time.
Plus, I use easyworksheet, but it's not the prettiest thing. This website is great for customizing your problems. It has multiple choice, mix up the problems, and starting number options. However, I just hate how it looks.
Our district uses studyisland.com. It isn't free but it is geared toward the standards. It was created as multiple choice. Although you can hide the multiple choice answer, sometimes the questions no longer make sense. For example, Which of the following is an irrational number? But there are no choices because you hid them.
math.com has an awesome generator for solving equations, systems, and quadratics. I don't feel it leaves enough room for the students' work, but that's the only drawback I can see.
What are your favorite online resources?