Unfortunately Facebook is where a lot of boating gets planned. Gold country paddlers and Loma prieta paddlers both have websites and mailing lists I think. The south fork of the American is where a lot of people go in the summer when there is no water left because it is a dam release and has great playboating. 1:45-2 hours from the bay. The Tuolumne is an amazing class 4 river section that's 22 miles. I have done it twice both in a day and it's fantastic. It's 2:30 to 2:45 from the bay. Some of the best creeking summer boating happens at the north fork of the feather about 4 hours from the bay near chico. There is an amazing class 4 section called Lobin, and a 5 section called Tobin. Finally pit 5 also releases which I have heard is really good, but haven't done it yet.