Bernina Thirty Somethings
Elna Heirloom Sewing Machines
Elna Sergers
Necchi Sewing Machine Club
Old Kenmore Sewing Machines
Old Pfaff Forum
Viking Sewing Machines pre-1980
Vintage Japan Sewing Machines
Vintage Sewing Machine Repair
Vintage Singers
We Fix It
I also belong to Treadle On but do not have their messages sent to me daily because they are too active with up to 30 messages a day! I subscribe to the digest format so once a day I get one email with all of the posts for each group for that day (if any). This gives me an overview of what's going on, if I can contribute, or when I just scan through because I don't have that model or problem. There are a few experts that chime in, always patient with the newbies, giving suggestion of what to try next. I can't help but admire their generous nature.
When it comes to books, they are more difficult to find, and usually deal with machines I'm not as interested in. BUT there are a few I do use (and like):
An online book, How to Refurbish Sewing Machines, A step-by-step guide for Singer models 66, 99, 15K & 201 is a series of pdf's that I have found very useful, especially the explanation of the tension assembly. And it's free. (edit: This is no longer a free item but you can purchase and help their community)
There is a list of recommended books at ISMAC that you might find interesting. You might find the whole ISMAC site interesting but I think it's poorly designed and laid out yet it still contains a wealth of information.
Sorry there are no pretty pictures of sewing machines or projects in this post but maybe you will take a look at some of these recommendations and learn something new as I have!