I find this kind of stuff fascinating- one source, one (official) art, many lineages and expressions. The biggest differences between styles seems to be where we start.
Some I have not found online, but probably exist - Shodokan (I put a link to one group), Iwama, Nishikawa, Tamura, Tada, Tissier, several offshoots of Shin Shin Toitsu Aikido? Seagal, what does he teach beginners? Of course, the answer is "Aikido" but we all do, just slightly differently.
We have many discussions here without much of a common framework. Even the list doesn't mean much - I saw a video of a sixth kyu USAF test in Florida with randori this past week, and there are independent dojos with ties to several organizations and teachers. What do you ask of your students? What do you feel is the best way to impart aikido to the majority of your students?