For reds that are widely available, lower in price and pretty consistant IMO:
Prices are general
Bogle Petite Sirah ($10)
Robert Mondavi Merlot and Cabernet
Cline Red Zinfandel ($15?)
Seghesio Sonoma Zinfandel ($15) - Usually the best Zin for under $20 year after year
Kendall Jackson Grand Reserve Cabernet (most of Kendall Jackson is not good, but this one is for the money ($20-$25) which is cheap for cabernet that's drinkable.
Some J Lohr
New Zealand Sauvignon Blancs are some of the best white wines for the money.
Others will hopefully chime in, and there are SO many wines but the above produces a lot and are easily available. Any decent store will have them or be able to suggest something.