Since you live in NorCal and probably visit the Delta you should buy a good holding anchor. The best is a box anchor. http://www.slideanchor.com/box.asp
At the least a danforth anchor will hold much better in a gravel or rocky bottomed lake. http://www.danforthanchors.com/
I personally like the plastic coated ones for comp boats as they protect the boat from accidental run ins. You will also need a chain, again the plastic ones work well, at the least galvanized, stainless is best $$ but either way you should invest in a stainless shackle. http://www.westmarine.com/webapp/wcs/stores/servlet/product/10001/-1/10001/50919/10001/519/242/5
You need at least 100 ft of anchor line on board but really should carry close to 200 of line, so you can tie front and rear.
Many people like the bungie anchors, and they have their time and place. Personally I do not like them as they can stretch enough to send your boat towards solid objects like rocks! I always kept one of the bungies on board, but used it less than 10% of the time.
How much anchor line you use is about a 5:1 ratio for a small boat in decent conditions. 7:1 in bad conditions. So if it is 10ft deep, set out 50 feet of line. Do you always have to abid by that rule no, but it is a good thing to know.
Edit: BTW it is the law that you must have an achor and line, along with bailing bucket, paddle, throwable, etc. I need to go and dive in the Putah Creek cove and rescue a few lost anchors
(Message edited by Peter_C on June 18, 2006)