That was the first site I had looked through and was disappointed that most races were 3 and 4 hours from SF. I did managed to find this http://www.beattheclock.us/
A low key race series that meets up every couple of weeks. I’m definitely putting that on my calendar.
Ncnca.org / road is the better spot. You have to search monthly but there’s Calaveras (16k) in May, Dunlap (30k) and Sattley (40k) in June, red Kite in July, Warnerville in August (38k), and Esparto in Sept (think it’s 30k).
Putah Creek Smackdown is free, Wednesdays bi-weekly in Winters, starting after daylight savings. Most weeks are 16k but there are a few 40k as well.
On top of those, there are also Beat the Clock series and one other that’s escaping me a the moment.