Here are some useful fishing websites that I visit often:

Dreamflows
http://www.dreamflows.com/flows.php?page=real&zone=canv&form=norm
For current and past information on flows for most rivers and streams in California.

StevenOjai
http://flyfishingthesierra.com/homepage.htm
An excellent resource for tons of information and maps about creeks, streams, and lakes in both the Eastern and Western Sierra Nevada.

Kiene’s Fly Shop Forums
http://www.kiene.com/forums/
An online forum for discussing all things fly fishing in Northern California.

Sportfishing Report
http://www.sportfishingreport.com/pages/freshwater.php?region=11
A site with a compilation of fishing reports that cover several bodies of water in California. The report is updated frequently although the body of water is often random.

Jon Baiocchi Fly Fishing News
http://jonbaiocchiflyfishingnews.blogspot.com/
Jon Baiocchi was a veteran guide that specialized in fly fishing Lake Davis, the NF Yuba River, the Yuba River, and many other streams and rivers in Northern California. Although he has since passed his blog continues to be a great resource that has archived several years of his outings and fishing reports.

Gilligan’s Guide Service
http://www.gilligansguideservice.com/blog/
Matt “Gilligan” Kole’s is a fly fishing guide that covers waters within the Truckee River area in addition to Pyramid Lake. He will frequently post fishing reports and updates about the area he services.

The Ecological Angler
http://www.ecoangler.com/index.html
Michael Carl’s site is a great resource for rivers and streams in California. I’ve bought and used several of the author’s publications for the Heritage Trout Challenge.